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Saeedi K, Szech M, Dluhy P, Salvail JZ, Morse KJ, Riemann H, Abrosimov NV, Notzel N, Litvinenko KL, Murdin BN, Thewalt ML. The push for a semiconductor-based quantum information technology has renewed interest in the spin states and optical transitions of shallow donors in silicon, including the donor bound exciton transitions in the near-infrared and the Rydberg, or hydrogenic, transitions in the mid-infrared. Litvinenko KL, Bowyer ET, Greenland PT, Stavrias N, Li J, Gwilliam R, Villis BJ, Matmon G, Pang MLY, Redlich B, Van Der Meer AFG, Pidgeon CR, Aeppli G, Murdin BN. Litvinenko KL, Pang M, Li J, Bowyer E, Engelkamp H, Shuman VB, Portsel LM, Lodygin AN, Astrov YA, Pavlov SG, Huebers H-W, Pidgeon CR, Murdin BN. Shallow donors in silicon are favorable candidates for the implementation of solid-state quantum computer architectures because of the promising combination of atomiclike coherence properties and scalability from the semiconductor manufacturing industry.
Bowyer ET, Villis BJ, Li J, Litvinenko KL, Murdin BN, Erfani M, Matmon G, Aeppli G, Ortega JM, Prazeres R, Dong L, Yu X. We report the characteristics of a simple complementary metal-oxide-semiconductor compatible terahertz detector device with low response time (nanoseconds) determined using a short-pulse, high intensity free-electron laser.
Huebers H-W, Pavlov SG, Lynch SA, Greenland T, Litvinenko KL, Murdin B, Redlich B, van der Meer AFG, Riemann H, Abrosimov NV, Becker P, Pohl H-J, Zhukavin RK, Shastin VN. Murdin BN, Li J, Pang ML, Bowyer ET, Litvinenko KL, Clowes SK, Engelkamp H, Pidgeon CR, Galbraith I, Abrosimov NV, Riemann H, Pavlov SG, Hubers HW, Murdin PG. Laboratory spectroscopy of atomic hydrogen in a magnetic flux density of 10(5)?T (1 gigagauss), the maximum observed on high-field magnetic white dwarfs, is impossible because practically available fields are about a thousand times less. Greenland PT, Lynch SA, van der Meer AFG, Murdin BN, Pidgeon CR, Redlich B, Vinh NQ, Aeppli G.
Litvinenko KL, Leontiadou MA, Li J, Clowes SK, Emeny MT, Ashley T, Pidgeon CR, Cohen LF, Murdin BN. Vinh NQ, Greenland PT, Litvinenko K, Redlich B, van der Meer AFG, Lynch SA, Warner M, Stoneham AM, Aeppli G, Paul DJ, Pidgeon CR, Murdin BN. PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 105 (31), pp. Litvinenko KL, Nikzad L, Pidgeon CR, Allam J, Cohen LF, Ashley T, Emeny M, Zawadzki W, Murdin BN. Litvinenko KL, Li J, Stavrias N, Meaney AJ, Christianen PCM, Engelkamp H, Homewood KP, Pidgeon CR, Murdin BN.
Greenland PT, Matmon G, Villis BJ, Bowyer ET, Li J, Murdin BN, van der Meer AFG, Redlich B, Pidgeon CR, Aeppli G. Murdin BN, Litvinenko K, Li J, Bowyer E, Pang M, Greenland PT, Villis B, Aeppli G, van der Meer AFG, Redlich B, Engelkamp H, Pidgeon CR. Vinh NQ, Redlich B, van der Meer AFG, Pidgeon CR, Greenland PT, Lynch SA, Aeppli G, Murdin BN.
Lynch SA, Thornton Greenland P, Van Der Meer AFG, Murdin BN, Pidgeon CR, Redlich B, Vinh NQ, Aeppli G. It has long been known that shallow donors such as phosphorous and the other group-V elements, have a hydrogen-like optical spectrum. Leontiadou MA, Litvinenko KL, Gilbertson AM, Pidgeon CR, Branford WR, Cohen LF, Fearn M, Ashley T, Emeny MT, Murdin BN, Clowes SK.
Wittmann B, Danilov SN, Bel'kov VV, Tarasenko SA, Novik EG, Buhmann H, Bruene C, Molenkamp LW, Kvon ZD, Mikhailov NN, Dvoretsky SA, Vinh NQ, van der Meer AFG, Murdin B, Ganichev SD.
Danilov SN, Wittmann B, Olbrich P, Eder W, Prettl W, Golub LE, Beregulin EV, Kvon ZD, Mikhailov NN, Dvoretsky SA, Shalygin VA, Vinh NQ, van der Meer AFG, Murdin B, Ganichev SD. Wittmann B, Golub LE, Danilov SN, Karch J, Reitmaier C, Kvon ZD, Vinh NQ, van der Meer AFG, Murdin B, Ganichev SD.
Weber W, Golub LE, Danilov SN, Karch J, Reitmaier C, Wittmann B, Bel'kov VV, Ivchenko EL, Kvon ZD, Vinh NQ, van der Meer AFG, Murdin B, Ganichev SD. Rauter P, Fromherz T, Vinh NQ, Murdin BN, Phillips JP, Pidgeon CR, Diehl L, Dehlinger G, Gruetzmacher D, Zhao M, Ni W-X, Bauer G.
Califano M, Vinh NQ, Phillips PJ, Ikonic Z, Kelsall RW, Harrison P, Pidgeon CR, Murdin BN, Paul DJ, Townsend P, Zhang J, Ross IM, Cullis AG.
Jin SR, Ahmad CN, Sweeney SJ, Adams AR, Murdin BN, Page H, Marcadet X, Sirtori C, Tomic S.
Rauter P, Fromherz T, Bauer G, Vinh NQ, Murdin BN, Phillips JP, Pidgeon CR, Diehl L, Dehlinger G, Gruetzmacher D. Lynch SA, Paul DJ, Townsend P, Matmon G, Suet Z, Kelsall RW, Ikonic Z, Harrison P, Zhang J, Norris DJ, Cullis AG, Pidgeon CR, Murzyn P, Murdin B, Bain M, Gamble HS, Zhao M, Ni W-X. Jefferson PH, Veal TD, Piper LFJ, Bennett BR, McConville CF, Murdin BN, Buckle L, Smith GW, Ashley T.
Roither J, Pichler S, Kovalenko MV, Heiss W, Feychuk P, Panchuk O, Allam J, Murdin BN. Litvinenko KL, Murdin BN, Allam J, Pidgeon CR, Zhang T, Harris JJ, Cohen LF, Eustace DA, McComb DW.
Litvinenko KL, Murdin BN, Allam J, Pidgeon CR, Bird M, Morris K, Branford W, Clowes SK, Cohen LF, Ashley T, Buckle L.
Murdin BN, Litvinenko K, Clarke DG, Pidgeon CR, Murzyn P, Phillips PJ, Carder D, Berden G, Redlich B, van der Meer AF, Clowes S, Harris JJ, Cohen LF, Ashley T, Buckle L. We have used two-color time-resolved spectroscopy to measure the relaxation of electron spin polarizations in a bulk semiconductor. Determination of the electronic energy vs momentum relationship in semiconductors is essential for the prediction of almost all of their properties.
Rauter P, Fromherz T, Bauer G, Vinh NQ, Phillips PJ, Pidgeon CR, Murdin BN, Diehl L, Dehlinger G, Grutzmacher D. O'Brien K, Adams AR, Sweeney SJ, Jin SR, Ahmad CN, Murdin BN, Canedy CL, Vurgaftman I, Meyer JR. The results from high-pressure and low-temperature measurements on mid-infrared type-II W-structure lasers suggest that Auger recombination is the major loss process that prevents their continuous-wave operation at room temperature. Ganichev SD, Schneider P, Bel'kov VV, Ivchenko EL, Tarasenko SA, Wegscheider W, Weiss D, Schuh D, Murdin BN, Phillips PJ, Pidgeon CR, Clarke DG, Merrick M, Murzyn P, Beregulin EV, Prettl W. Leontiadou MA, Litvinenko KL, Clowes SK, Springholz G, Schwarzl T, Eibelhuber M, Heiss W, Pidgeon CR, Murdin BN. We report significant temperature dependence of the transverse electron g*-factor in symmetric lead chalcogenide multi-quantum wells (MQWs).
AIP Conference Proceedings, Seoul, South Korea: ICPS2010, 30th International Conference on the Physics of Semiconductors 1399, pp.
We have investigated the effect of an external magnetic field on the electron spin lifetime in narrow gap semiconductors (NGS). Lynch SA, Greenland PT, van der Meer AFG, Murdin BN, Pidgeon CR, Redlich B, Nguyen QV, Aeppli G.
Danilov SN, Wittmann B, Olbrich P, Prettl W, Golub LE, Beregulin EV, Kvon Z-D, Mikhailov NN, Dvoretsky SA, Shalygin VA, Vinh NQ, van der Meer AFG, Murdin B, Ganichev SD. 2009 34TH INTERNATIONAL CONFERENCE ON INFRARED, MILLIMETER, AND TERAHERTZ WAVES, VOLS 1 AND 2, Busan, SOUTH KOREA: 34th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz 2009), pp. Lynch SA, Greenland PT, Vinh NQ, Litvinenko K, Redlich B, van der Meer L, Warner M, Stoneham AM, Aeppli G, Pidgeon CR, Murdin BN. 2008 5TH IEEE INTERNATIONAL CONFERENCE ON GROUP IV PHOTONICS, Sorrento, ITALY: 5th IEEE International Conference on Group IV Photonics, pp.
Pidgeon CR, Litvinenko KL, Nikzad L, Allam J, Cohen LF, Ashley T, Emeny M, Murdin BN. NARROW GAP SEMICONDUCTORS 2007, Guildford, ENGLAND: 13th International Conference on Narrow Gap Semiconductors 119, pp. Litvinenko KL, Murdin BN, Clowes SK, Nikzad L, Allam J, Pidgeon CR, Branford W, Cohen LF, Ashley T, Buckle L. JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM, Maui, HI: 4th International School and Conference on Spintronics and Quantum Information Technology (Spintech IV) 20 (6), pp. Litvinenko KL, Nikzad L, Allam J, Murdin BN, Pidgeon CR, Harris JJ, Zhang T, Cohen LF. O'Brien K, Sweeney SJ, Adams AR, Jin SR, Ahmad CN, Murdin BN, Salhi A, Rouillard Y, Joullie A.
PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, Barcelona, SPAIN: 12th International Conference on High Pressure Semiconductor Physics (HPSP-12) 244 (1), pp. Zhao M, Karim A, Ni W-X, Pidgeon CR, Phillips PJ, Carder D, Murdin BN, Fromherz T, Paul DJ. JOURNAL OF LUMINESCENCE, Nice, FRANCE: Symposium on Si-based Photonics held at the EMRS 2006 Conference 121 (2), pp. Ashley T, Buckle L, Smith GW, Murdin BN, Jefferson PH, Piper LFJ, Veal TD, McConville CF. Infrared Technology and Applications XXXII, Pts 1and 2, Kissimmee, FL: 32nd Conference on Infrared Technology and Applications 6206, pp.
Professor Chris Fry awarded the Fellowship ad hominem in recognition of his lifetime contribution to the advancement of surgical education and training. President of The Royal College of Surgeons of Edinburgh, Mr Ian Ritchie said: “RCSEd has a long history of innovation and advancement and Professor Fry’s contribution exemplifies this quality.
Dr Simon Archer and Prof Derk-Jan Dijik from the Sleep Research Centre look into how sleeping works in space and how there's more to it than just nodding off. World-renowned academics will be serving up pint-sized measures of their cutting edge research in a ground-breaking project to hit Guildford pubs. New research at Surrey suggests disrupted sleep patterns could have more impact on some measures of women's performance than men's. With clocks set to spring forward on Sunday 27 March, read our top tips to help minimise the impact of an hour’s less sleep. From modern science fiction to famous political texts, discover which books our academics recommend, then take the quiz to find out which one you should try first.
A new vaccine, which aims to enable our immune systems to fight against advanced cancer, is due to be trialled at the University of Surrey. A new class of X-ray sensor – in which there is a blend of poly(triarylamine) (PTAA) and 6,13-bis(triisopropylsilylethynyl) (TIPS)-pentacene in the active layer of a diode structure – has been developed. Duarte DD, Lipp JD, Schneider A, Seller P, Veale MC, Wilson MD, Baker MA, Sellin PJ.
NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, 806, pp. Ciavatti A, Capria E, Fraleoni-Morgera A, Tromba G, Dreossi D, Sellin PJ, Cosseddu P, Bonfiglio A, Fraboni B. Bell SJ, Baker MA, Duarte DD, Schneider A, Seller P, Sellin PJ, Veale MC, Wilson MD. Alruhaili A, Sellin PJ, Lohstroh A, Boothman V, Veeramani P, Veale MC, Sawhney KJS, Kachkanov V. We employed measurement of the Pockels electro-optic effect to study the electric field and space charge dynamics in semi-insulating CdTe doped with indium. Alruhaili A, Sellin PJ, Lohstroh A, Veeramani P, Kazemi S, Veale MC, Sawhney KJS, Kachkanov V. Bell SJ, Baker MA, Chen H, Marthandam P, Perumal V, Schneider A, Seller P, Sellin PJ, Veale MC, Wilson MD. Cadmium zinc telluride (CdZnTe) is now established as a popular choice of sensor for the detection of ?-rays and hard x-rays, leading to its adoption in security, medical and scientific applications. Duarte DD, Bell SJ, Lipp J, Schneider A, Seller P, Veale MC, Wilson MD, Baker MA, Sellin PJ, Kachkanov V, Sawhney KJS. Large area detectors capable of operating with high detection efficiency at energies above 30 keV are required in many contemporary X-ray imaging applications. Semiconducting polymer X-radiation detectors are a completely new family of low-cost radiation detectors with potential application as beam monitors or dosimeters. Recently, a new family of low-cost x-radiation detectors have been developed, based on semiconducting polymer diodes, which are easy to process, mechanically flexible, relatively inexpensive, and able to cover large areas.
We studied polarization in semi-insulating detector-grade cadmium zinc telluride without and with high optical flux. The electrical characteristics and fast neutron response of a High Temperature Chemical Vapour Deposition (HTCVD) grown semi-insulating bulk SiC wafer has been measured. The performance of single crystal CdZnTe radiation detectors is dependent on both the bulk and the surface properties of the material.
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 729, pp. A digital pulse-shape discrimination algorithm for the identification of multi-site ?-ray interactions in coplanar CdZnTe detectors has been developed.
Wilson MD, Bell SJ, Cernik RJ, Christodoulou C, Egan CK, O'Flynn D, Jacques S, Pani S, Scuffham J, Seller P, Sellin PJ, Speller R, Veale MC.



A pixellated CdTe detector system comprising 2x2 detector modules has been developed for high energy spectroscopic X-ray imaging applications and has an active area of 16 cm2. Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 695, pp. We report on preliminary alpha particle and X-ray measurements on a number of prototype GaN PIN diodes.
Scuffham JW, Scuffham JW, Sellin PJ, Wilson MD, Seller P, Veale MC, Jacquesd SDM, Cernik RJ. A Cadmium Telluride (CdTe) detector has been developed for multiple-radioisotope SPECT imaging.
Choubey A, Veeramani P, Pym ATG, Mullins JT, Sellin PJ, Brinkman AW, Radley I, Basu A, Tanner BK.
Growth by the Multi-tube Physical Vapour Transport technique and characterisation of bulk (Cd,Zn)Te is described. Schirru F, Lohstroh A, Sellin J, Nara Singh S, Scruton L, Bentley A, Fox P, Banu A, McCleskey M, Roeder T, Simmons E, Alharbi A, Trache L, Freer M, Parker D, Banu A. We have studied the effects of electrode fabrication and detector capacitance on the time resolution of large area electronic grade polycrystalline chemical vapour deposited diamond sensors that are suitable for time of flight measurements of heavy ions at relativistic velocities.
Scuffham JW, Wilson MD, Pani S, Duarte DD, Veale MC, Bell S, Seller P, Sellin PJ, Cernik RJ. Simultaneous dual-tracer brain imaging has the potential to shorten patient pathways in the diagnosis of neurodegenerative diseases, but the poor spectral resolution of conventional gamma cameras limits the utility of this technique.
Semiconducting polymers have previously been used as the transduction material in x-ray dosimeters, but these devices have a rather low detection sensitivity because of the low x-ray attenuation efficiency of the organic active layer. Allwork C, Kitou D, Chaudhuri S, Sellin PJ, Seller P, Veale MC, Tartoni N, Veeramani P. Recent advances in the growth of CdZnTe material have allowed the development of small pixel, spectroscopic, X-ray imaging detectors.
A significant reduction in the electrical percolation threshold is achieved by locking carbon nanotubes (CNTs) in a predominantly hexagonally close-packed (HCP) colloidal crystal lattice of partially plasticized latex particles. Seller P, Bell S, Cernik RJ, Christodoulou C, Egan CK, Gaskin JA, Jacques S, Pani S, Ramsey BD, Reid C, Sellin PJ, Scuffham JW, Speller RD, Wilson MD, Veale MC.
We have developed a pixellated high energy X-ray detector instrument to be used in a variety of imaging applications. Veale MC, Bell SJ, Jones LL, Seller P, Wilson MD, Allwork C, Kitou D, Sellin PJ, Veeramani P, Cernik RC.
Lohstroh A, Sellin PJ, Gkoumas S, Al-Barakaty H, Veeramani P, Ozsan ME, Prekas G, Veale MC, Parkin JM, Davies AW. Take a look inside the pioneering new School of Veterinary Medicine at the University of Surrey and see pictures of our first-year student vets in practice. Following an initial intake of 48 student vets in 2014, the Vet School recently welcomed its second cohort of 120 students. The University of Surrey has officially launched an ?11m Veterinary Pathology Centre which will provide a focus for pathology research, education and commercial activity. Learn more about the Vet School’s Professor Noel Fitzpatrick - star of Channel 4's The Supervet - in our video interview by Jim Al-Khalili, Surrey’s Surrey Professor of Physics and Public Engagement in Science. A collaboration between the University of Surrey and the Kennel Club aims to investigate how German Shepherds stand and move, potentially revealing information that could benefit all dogs.
Researchers from the University of Surrey and the University of Nottingham set out to determine which types of nutritional supplements were used in dressage and eventing horses, and the reasons behind owners using them.
Surrey’s Student Learning Advisors offer tips and advice on the things you can do throughout the year to help you make the most of your study time. The deepest group V donor in silicon, bismuth, has a large zero-field ground state hyperfine splitting, comparable to that of rubidium, upon which the now-ubiquitous rubidium atomic clock time standard is based. All rights reserved.The ability to control dynamics of quantum states by optical interference, and subsequent electrical read-out, is crucial for solid state quantum technologies. Quantum processing schemes require (among other things) controlled information transfer for readout.
Local symmetry was determined by fitting crystal field parameters (CFPs), corresponding to various common symmetries, to the ground state splitting determined by photoluminescence measurements.
The main difference is that while the spectrum of atomic hydrogen lies in the visible band, the spectrum of shallow donors in silicon is downshifted to the THz frequency band.
We exploit the photon echo as an experimental tool to investigate the quantum coherence properties of excited donor Rydberg states of phosphorus in silicon. The circularly polarized pump beam induces a polarization either by direct excitation from the valence band, or by free-carrier (Drude) absorption when tuned to an energy below the band gap.
In materials useful for mid-infrared applications, the simplest parabolic band approximations are usually insufficient. The g*-factor values were extracted from the electron Larmor precessions recorded by means of a circularly polarized pump probe technique under the influence of transverse external magnetic field (Voigt geometry) in the temperature range between 10 and 150K. In zero field, we show that the D'yakonov-Perel process dominates even at low temperatures.
I have a deep commitment to surgical training through research supervision, preparation for membership examinations and promoting a central role for an understanding of physiological principles.
University of Edinburgh, Thesis entitled ‘Proton radioactivity measurements using a double-sided silicon strip detector’, Oct 1988 - Jan 1992                    Research InterestsDevelopment and characterisation of high-Z compound semiconductor materials (eg.
The crystalline pentacene provides a fast route for charge carriers and leads to enhanced performance of the sensor.
One of the most promising materials is cadmium zinc telluride (CdZnTe or CZT), which has been demonstrated in homeland security, medical imaging, astrophysics and industrial analysis applications. The main material limitation is associated with the poor charge transport properties of holes. There are still many technical challenges involving the deposition of high-quality, uniform metal contacts on CdZnTe.
The properties of high Z compound semiconductors, such as CdTe, make them ideally suitable to these applications.
These detectors are easy to process, mechanically flexible, relatively inexpensive, and able to cover large areas.
To test their potential for radiotherapy applications such as beam monitors or dosimeters, as an alternative to the use of solid-state inorganic detectors, we present the direct detection of 6 MV x-rays from a medical linear accelerator using a thick film, semiconducting polymer detector. We employed the Pockels electro-optic effect combined with two perpendicular sources of light.
Current-Voltage measurements demonstrated a low leakage current in the region of 10 to 10 A with a bulk resistivity of at least 10-10 ?.cm. After single crystal fabrication and mechanical polishing, modification of the surface to remove damage and reduce the surface leakage current is generally achieved through chemical etching followed by a passivation treatment. Current - Voltage measurements demonstrated a low leakage current in the region of 10-10 to 10-12 A with a bulk resistivity of at least 1012 - 1013 ?.cm. The algorithm is used to suppress the Compton continuum in ?-ray spectroscopy measurements by rejecting the single-site events. The detector modules are made from the HEXITEC 80x80 ASIC and 1 mm thick CdTe with Al-Schottky contacts. The aim of the study was to investigate the potential use of GAN based radiation detectors for radiation hard, high temperature, solar blind space applications.
Lately these sensors have been investigated for Time of Flight Positron Emission Tomography (ToF-PET) applications, where very good coincidence time resolution of the order of hundreds of picoseconds imply spatial resolution of the order of cm in the image reconstruction. The 22 cm detector has 8080 pixels on a 250 mm pitch and a three-side buttable design so that it can be tiled into larger arrays. The crystalline perfection and uniformity of zinc content have been mapped by infra-red transmission and microscopy, X-ray diffraction and photoluminescence.
We conclude that, once further refinements are made, a large area time of flight detection system using polycrystalline diamond detectors would be able to provide time resolutions better than 40 ps, approaching the requirement for particle-identification in relativistic fragmentation experiments, such as those at the facility for antiproton and ion research, FAIR.
Solid state detectors offer improved capability to distinguish between two radioisotopes, but the technology has yet to be fully evaluated in the field of scintigraphic neuroimaging.
Here, we demonstrate a way to overcome this limitation through the introduction of high density nanoparticles having a high atomic number (Z) to increase the x-ray attenuation.
The mechanical flexibility of the polymer is not sacrificed when the inorganic nanoparticles are incorporated.
These detectors have applications in a diverse range of fields such as medical, security and industrial sectors. Contrary to other widely used latex processing where CNTs are randomly distributed within the latex matrix, for the first time, we show that excluding CNTs from occupying the interior volume of the latex particles promotes the formation of a nonrandom segregated network. The instrument consists of either a Cadmium Zinc Telluride or Cadmium Telluride (Cd(Zn)Te) detector bump-bonded to a large area ASIC and packaged with a high performance data acquisition system. I chaired the International Conference on Narrow Gap Semiconductors, here in Guildford in 2007. Here we show that the ground state hyperfine populations of bismuth can be read out using the mid-infrared Rydberg transitions, analogous to the optical readout of the rubidium ground state populations upon which rubidium clock technology is based.
Ramsey interference has been successfully observed for spins in silicon and nitrogen vacancy centres in diamond, and for orbital motion in InAs quantum dots.
Here we demonstrate controlled electron tunneling at 10 K from P to Sb impurities and vice versa with the assistance of resonant terahertz photons.
The detector has an enhanced response over narrow bands, most notably at 9.5 THz, with a continuum response at higher frequencies. Here we demonstrate Lyman series spectra for phosphorus impurities in silicon up to the equivalent field, which is scaled to 32.8?T by the effective mass and dielectric constant. This is a direct consequence of the reduced Coulomb attraction seen by the loosely bound electron because the core electrons shield the positive donor atom nucleus, and because the electron is now moving in a dielectric material. We find that the spin relaxation time, measured with picosecond time resolution by resonant induced Faraday rotation in both cases, increases in the presence of photogenerated holes.
However relatively straight-forward numerical techniques based on the k.p method can yield good predictions for the bandstructure.
The reported g*-factor values are in good agreement with theoretical predictions and available low temperature experimental data. In the Faraday configuration it is suppressed and the spin lifetime increases with field, whereas in Voigt configuration, the additional Margulis-Margulis process, which is particularly effective in NGS, shortens the spin lifetime considerably. While the characteristics of the 2.37 mu m devices are much improved by the suppression of the CHSH Auger process, since its spin-orbit splitting energy is greater than its band gap, other important Auger processes such as CHHL and CHCC persist. These applications have demanding energy and spatial resolution requirements that are not always met by the metal contacts deposited on the CdZnTe. The motivation of this work is to investigate the performance characteristics of a detector fabricated with a drift ring geometry that is insensitive to the transport of holes.
A detailed understanding of the interface between the bulk CdZnTe and the metal contacts is required for improvements to be made. The STFC Rutherford Appleton Laboratory has developed a small pixel CdTe detector with 80 ? 80 pixels on a 250 ?m pitch. However, their x-ray photocurrents are typically low as, being composed of elements of low atomic number (Z), they attenuate x-rays weakly.
A beam of red light or an infrared laser was applied parallel to the direction of the electric field acting as a source of electron-hole pairs.
Alpha particle spectroscopy measurements demonstrated an electron charge collection efficiency of up to 90% with reasonable reproducibility of the acquired spectra.
In this work, CdZnTe single crystals have been chemically etched using a bromine in methanol (BM) treatment. The very fast rise time typical of the avalanche discharge improves the time resolution, but can be limited by the readout electronics and the technology used to construct the device. The detector is termed hyperspectral as it measures the energy of every photon that interacts in the CdTe to give fully spectroscopic information from 5-200 keV in each pixel. We present imaging results for a new small-pixel CdTe detector in simultaneous dual-radioisotope scintigraphy of a brain phantom containing Tc-99m and I-123.
As the size of the pixels decreases relative to the detector thickness, the probability that charge is shared between multiple pixels increases due to the non zero width of the charge clouds drifting through the detector.
The electrical percolation threshold is four times lower in an ordered segregated network made with colloidal particles near their glass transition temperature (T(g)) in comparison to in a random network made with particles at a temperature well above the T(g). We further use these transitions to demonstrate strong population pumping by resonant excitation of the bound exciton transitions, suggesting several possible approaches to a solid-state atomic clock using bismuth in silicon, or eventually in enriched (28)Si. Here we demonstrate terahertz optical excitation, manipulation and destruction via Ramsey interference of orbital wavepackets in Si:P with electrical read-out. Using such a device, the dynamics of donors in silicon can be explored, a system which has great potential for quantum information processing.


The spectra reproduce the high-field theory for free hydrogen, with quadratic Zeeman splitting and strong mixing of spherical harmonics.
We find that both Dy and Tm ions are in a Si substitution site with local tetragonal symmetry. While spectroscopy has already revealed much about the energy level structure, very little was known about the temporal dynamics of the system until now.
The theoretical bandstructures can be compared with experiment using magneto-optics and magneto-transport, but one of the most useful tools for controllably tuning the system is hydrostatic stress. Although temperature tuning of lead salt laser emission wavelengths has been the method of choice in these systems for many years, we demonstrate that temperature can also be used to modulate g*, and hence the spin lifetime in lead salt QW spintronic devices. The spin dynamics are found to be very sensitive to both the magnitude and direction of the magnetic field.
In the larger band gap 2.11 mu m devices, an increase in threshold current with pressure is observed suggesting that CHSH Auger is present in these devices at atmospheric pressure and contributes to performance degradation at these shorter wavelengths. To improve the contacts, the interface formed between metal and semiconductor during contact deposition must be better understood.
The performance of a prototype Ohmic CdTe drift ring detector fabricated by Acrorad with 3 drift rings is reported; measurements include room temperature current voltage characteristics (IV) and spectroscopic performance.
To understand these complex interfaces, a range of complementary materials characterization techniques have been employed, including x-ray photoelectron spectroscopy depth profiling, focused ion beam cross section imaging and energy dispersive x-ray spectroscopy. Historically, these detectors have included a 200 ?m wide guard band around the pixelated anode to reduce the effect of defects in the crystal edge. Here, the addition of high-Z nanoparticles is used to increase the x-ray attenuation without sacrificing the attractive properties of the host polymer. The sensitivity of the diode was found to range from 13 to 20 nC mGy -1 cm-3, for operating voltages from -50 to -150 V, respectively.
Infrared radiation from the monochromator illuminated the sample perpendicular to the direction of the electric field and changed the occupation of deep levels and therefore the depth profile of the bulk electric field. Evidence of (incident particle) rate dependent polarisation was seen following a constant applied bias combined with alpha irradiation over a period of time (order of tens of minutes). The method is also very useful for background reduction in the neutrinoless double beta-decay experiments for which coplanar CdZnTe detectors are of interest.
The single HEXITEC 80x80 detectors have an average energy resolution (FWHM) of 800 eV at 59.9 keV. Au ohmic contacts were applied to the top of the GaN layer and the bottom of the substrate.
In this work the parameters of the equivalent circuit of the device that directly affect the pulse shape, namely the quenching resistance and capacitance and the diode and parasitic capacitances, were calculated. The detector has been tested for applications in multipleradioisotope SPECT imaging using a 1mm diameter pinhole configuration and standard phantom test objects containing Tc-99m, I-123 and Ga-67. The material exhibits a resistivity in the 2?10 9 ?cm range and planar devices fabricated from this material have shown electron mobility lifetime products of 4.07?10 -3 cm 2 V -1. In a systematic study under these conditions, we demonstrate that the time resolution is limited by detector capacitance and energy deposition in the sensors.
Quantitative comparison is made with images of the same phantom obtained using a conventional gamma camera.
These charge sharing events will result in a degradation of the spectroscopic performance of detectors and must be considered when analyzing the detector response. This method allows for a highly reproducible way to fabricate robust, stretchable, and electrically conducting thin films with significantly improved transparency and lattice percolation at a very low CNT inclusion which may find applications in flexible and stretchable electronics as well as other stretchable technologies.
This system uses a relatively simple wire-bonded interconnection scheme but this is being upgraded to allow multiple modules to be used with very small dead space. We show milliradian control over the wavefunction phase for the two-level system formed by the 1s and 2p states.
They show the way for experiments on He and H(2) analogues, and for investigation of He(2), a bound molecule predicted under extreme field conditions. Knowledge of rare-earth ion symmetry is important in maximising the number of optically active centres and for quantum technology applications where local symmetry can be used to control decoherence.
We have used THz pulses from the FELIX free electron laser to probe these hydrogen-like levels.
The strain modifies the bandstructure in a rather s imple way, principally by a linear increase in the fundamental gap, and thus it can be used to separate out effects that depend on bandgap. This higher mobility is correlated with a fourfold increase in the X-ray detection sensitivity in the PTAA:TIPS-pentacene devices.
Gold has a work function closely matching that of high resistivity CdZnTe and is a popular choice of contact metal. We have shown that the thermally activated depolarization cannot be explained by the conventional model used for the description of space charge formation so far and an alternative model involving a recombination level was suggested and successfully used. The data shows that the energy resolution of the detector is limited by leakage current which is a combination of bulk and surface leakage currents. The latest version of the detector ASIC is capable of four-side butting that allows the tiling of N ? N flat panel arrays. Two types of nanoparticles (NPs) are compared: metallic tantalum and electrically insulating bismuth oxide. Spectral measurements of the Pockels effect were used to determine energy levels responsible for polarization and to find the optimal wavelength for optical depolarization of the detectors. The ability of the wafer to detect fast neutrons was demonstrated and a comparison drawn with the MCNPX simulated response of a bulk SiC device. Angle resolved XPS and sputter depth profiling has been employed to characterize the surfaces for the different exposure conditions.
The detector has an average pixel energy resolution (FWHM) of 0.75% at the I-123 photopeak of 159 keV. We show that the CdTe detector offers improved scatter rejection and greatly reduced cross-talk between the energy windows.
In this paper charge sharing and charge loss in a 250 ?m m pitch CdZnTe pixel detector has been investigated using a mono-chromatic X-ray beam at the Diamond Light Source, U.K.
For instance, our technology is particularly apt for touch screen applications, where one needs homogeneous distribution of the conductive filler throughout the matrix.
The results have been verified by all-optical echo detection methods, sensitive only to coherent excitations in the sample. By exploiting the well-known pump-probe technique we have measured the characteristic lifetimes of the excited Rydberg states and found them to be of the order 200 ps. A large literature has built up on the study of near-infrared optoelectronic devices under pressure. Gold contacts are often formed by electroless deposition however this forms a complex interface.
The energy resolution was studied as a function of incident X-ray position with an X-ray microbeam at the Diamond Light Source.
To limit the dead space between modules to the width of one pixel, edgeless detector geometries have been developed where the active volume of the detector extends to the physical edge of the crystal. The detection sensitivity of 5 µm thick semiconducting poly([9,9-dioctylfluorenyl-2,7-diyl]-co-bithiophene) diodes containing tantalum NPs is four times greater than that for the analogous NP-free devices; it is approximately double that of diodes containing an equal volume of bismuth oxide NPs. Comparing the MCNPX simulated response of a bulk SiC device to that of a silicon device suggests a superior ability to detect fast neutrons with an intrinsic efficiency 1.7 times that of silicon.
A Te rich surface layer was formed for all exposures and the layer thickness was found to be independent of exposure time. The spacing between the tiled detector modules is 150 ? m which results in an inactive area equivalent to 3 pixels, including the guard ring on the edge of the detectors. All devices showed good diode behaviour with reverse leakage currents in the tens to hundreds of micro-amp range. We demonstrate the system's capability of resolving spatial features of 2 mm, although the spatial resolution of the detector is limited only by the pixel size and pinhole magnification factor.
In addition, the new detector is able to resolve low-energy fluorescence x-rays from the source, which could be incorporated into SPECT reconstruction algorithms.
The experiments open a route to exploitation of donors in silicon for atom trap physics, with concomitant potential for quantum computing schemes, which rely on orbital superpositions to, for example, gate the magnetic exchange interactions between impurities.
Then, by making subtle changes to the geometry of the pump-probe experimental setup we demonstrate the existence of a THz photon echo. These have been used to establish the variations of the radiative and non-radiative Auger recombination processes with band structure. The prior CdZnTe surface preparation, such as mechanical or chemo-mechanical polishing, and electroless deposition parameters, such as gold chloride solution temperature, play important roles in the formation of the interface and are the subject of the presented work. Different ring biasing schemes were investigated and the results show that by increasing the lateral field (i.e. The spectroscopic performance of an edgeless CdTe detector bump bonded to the HEXITEC ASIC was tested with sealed radiation sources and compared with a monochromatic X-ray micro-beam mapping measurements made at the Diamond Light Source, U.K.
The x-ray induced photocurrent output of the diodes increases with an increased concentration of NPs. The enriched Te layer thickness was accurately determined by calibrating the sputter rate against a CdTe layer of known thickness. The modular detector configuration demonstrates the potential to create large area detector arrays in the future.
These characteristics are superior to alternative detectors currently in use in clinical SPECT systems. Details of the planned development of the detector into a clinical demonstrator are discussed.
The photon echo is a purely quantum phenomenon with no classical analogue, and it allows us to study the quantum state of the donor electron. The results predict that III-V mid-IR lasers with direct band gaps less than the spin-orbit gap should have threshold current densities less than the near-IR lasers based on InP or GaAs. Techniques such as focused ion beam (FIB) cross section imaging, transmission electron microscopy (TEM), energy dispersive x-ray spectroscopy (EDS), x-ray photoelectron spectroscopy (XPS) and current - voltage (I-V) analysis have been used to characterize the interface. Trace amounts of indium were found, in the form of an indium-gold compound, or possibly indium oxide.
However, contrary to the results of theoretical x-ray attenuation calculations, the experimental current output is higher for the lower-Z tantalum diodes than the bismuth oxide diodes, at the same concentration of NP loading. The possibility of detecting x-rays with energies relevant to medical oncology applications opens up the potential for these polymer detectors to be used in detection and imaging applications using medical x-ray beams.
When exposed to a 5.5 MeV alpha particle source, the devices showed a spectroscopic response with energy resolutions of ?25% FWHM at room temperature (RT) and 10 V bias and 20% FWHM at -50 °C. When imaging multiple radioisotopes simultaneously, we show that there is very little cross-talk between adjacent photopeaks, leading to superior image contrast. We then show, using the photon echo, that it is possible to create a coherent superposition of the ground and excited state of the donor.
This result is likely due to the higher tantalum NP electrical conductivity, which increases charge transport through the semiconducting polymer, leading to increased diode conductivity.
The BM etched surfaces have subsequently been passivated in a 30 wt.% H2O2 solution employing exposure time of 15 s. The detector is also capable of resolving fluorescence x-rays from the radioactive source, which could be used to improve image count statistics or derive information about the attenuation properties of the source. Measuring the photon echo is important because it can also be used to measure a second important characteristic lifetime of the silicon-donor system, the phase decoherence time.
Clearly high-pressure techniques provide exciting opportunities for the study of mid-infrared devices.
Where the deposition occurred at elevated temperature, the deposited contacts were found to produce a greater leakage current and suffered from increased subsurface voiding due to the formation of cadmium chloride. The anode heterojunction, formed by a single stage electroless gold deposition, was thinner and exhibited a simpler structure of gold and tellurium oxide. The oxide layer thickness has been calculated using two standard XPS methodologies, based on the Beer-Lambert expression. The performance presented here, and the ability to tile the detector modules to create a clinically useful field of view, makes this technology a strong candidate to be used in future solid-state SPECT cameras. The TeO2 thickness calculated from ARXPS data are slightly higher than the thickness obtained by the simplified Beer-Lambert expression.



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