BNL-90243-2009-CP

SNM Movement Detection/Radiation Sensors and Advanced Materials Portfolio Review CdMnTe (CMT) Gamma Ray Detectors

Aleksey Bolotnikov

Presented at the RadSensing 2009 Conference PNNL, Richland, WA

June 2-4, 2009

June 2009

Nonproliferation and National Security Department

Brookhaven National Laboratory P.O. Box 5000

Upton, NY 11973-5000 www.bnl.gov

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Office of Nonproliferation Research and Development

SNM Movement Detection / Radiation Sensors and Advanced Materials Portfolio Review

RadSensing2009

CdMnTe (CMT) Gamma Ray Detectors

June 2-4, 2009

Aleksey BolotnikovBrookhaven National Laboratory

June 4, 2009

2

Project Information

• Research Team:– G. Camarda, A. Hossain, G. Yang, K. Kim, R. Gul, Y. Cui, S. Egarievwe,

and R. James (BNL)– L. Li (Yinnel Tech, Inc.), A. Mycielski (Poland Institute of Physics),

A. Burger (Fisk University), J. Franc (Charles University)

• Sub-contractors (CMT suppliers during the first year):– Yinnel Tech, Inc., (USA) and Institute of Physics (Poland)

• Universities (CMT characterization):– Fisk University and Charles University (Czech Republic)

• Project started in April of 2008 (mid year start), project review last week

• Budget:– FY 2008 – $480K– FY 2009 – $485K– FY 2010 – $490K

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Project goals

• Develop CMT radiation detectors: – Demonstrate feasibility (Phase 1 is complete)– Improve material properties and device performance

• This project will lead to novel radiation detectors:– high detection efficiency– high energy-resolution– ambient-temperature operation– low production cost

• Such detectors are needed in areas of nonproliferation and national security for detection of SNM

4

Background

• Anticipating benefits of using CMT: – High homogeneity of crystal:

segregation coefficient of Mn in CdTe is ~1 (compared to 1.35 for Zn), which opens opportunity to grow large-volume uniform crystals

– High resistivity at less alloy %:5-6% of Mn increases the bandgap up to ~1.60 eV, which corresponds to bulk resistivity of 1010-1011 Ω·cm

– Less % of Mn alloy => better crystal quality => longer carrier lifetime

• Challenges:– Growth of high-quality single crystals:

Overcome potential twinning and secondary phase formation (Te inclusions)

Purification of MnFind right dopant (or dopants) to compensate shallow levels

-- Develop suitable device fabrication processes (try to adapt CZT technology methods)

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Alternative materials proposed for room-temperature semiconductor detectors

• HgI2 and TlBr are promising alternative materials for gamma-ray detectors but practical uses of these materials are not feasible at this time

• Among these candidates only CZT and CMT are close to their anticipated performances as semiconductor detectors

AlSb CdZnTe CdMnTe HgI2 TlBr

Density, g/cm3 4.3 5.8 5.8 6.4 7.6<Z> 32 49 49 62 58

Resistivity, ohm-cm 107 3x1010 3x1010 >1012 >1012

- chemically reactive- difficult to handle- toxic

TlBr HgI2CZT

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Technical approach

The project covers four development areas:

– Material growth – Material characterization – Device fabrication and testing– Material and detector improvements

During the first year, we tested CMT crystals provided by outside suppliers. This year, we will start growing CMT in our lab.

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Crystals from two suppliers

• Institute of Physics, Poland (Dr. A. Mycielski) – Small crystals cut from 2-3 mm thick wafers – V-doped (5x1015 – 4x1017 cm-3 )– Mn concentration 5-13 %– Annealed at 650 °C for 100 hours – Cd, Te = 5N-6N purity– Mn = 4N-5N

• Yinnel Tech, Inc. (Dr. Longxia Li), CZT grower– Three ingots – Indium doped (2.5 ppm, 4 ppm, 6 ppm)– Mn concentration 5%– Extra Cd, (Cd/CMT: 0, 2x10-4, 3.3x10-4)– Material purity: Cd, Te ~6N– Mn = 5N-6N– Ingots were grown at approximately the same

conditions and at the rate of 0.8 mm/hr

• Both vendors use a Low Pressure Bridgman Method

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Material characterizations and device fabrication

• Material characterizations:– Optical and IR microscopy– I-V curve measurement– X-ray diffraction topography (NSLS)– High-resolution X-ray mapping (NSLS)– X- and gamma-ray measurements – Photoluminescence (PL) measurement– Deep-Level Transient Spectroscopy

(DLTS)– Etch Pits Analysis (EPD)

• We use the same device fabrication techniques originally developed for CdZnTe detectors: crystals were polished and then etched for 2~5 minutes in a 2% or a 5% bromine methanol solution

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Results from testing V-doped samples

• Over 30 samples with typical thickness of 2-3 mm were tested

• Overall, V-doped samples had low performance, although some improvements were observed over a Year I

• Specific results:– The best electron mu-tau was ~10-4 cm2/V (likely related to the deep levels

associated with vanadium dopant) – Typical mobility of 200 - 400 cm2/V·s (high concentration of impurities or

dislocations?)– Resistivity is on a low side (107 - 1010 Ω·cm)– The very first samples had lots of twins and inclusions– More recent samples were free of twins and Te inclusions (annealed

crystals)– High concentrations of dislocations and cellular structures– Crystal strains

• Properties of V-doped CMT samples may not be satisfactory for radiation detectors

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Spectral Response of V-doped Samples

• V-doped CMT– 9x9x2 mm3 Cd0.94Mn0.06Te– Vanadium doped (5×1016 cm-3)– Resistivity: 3.2×1010 Ω⋅cm

Am-241 peakGain: 1k, Shapping time: 2 us

Electron mu-tau 2x10-4 cm2/V

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After etching with EAg-1,grain boundaries and twinsare visible. Dark and shinyregions correspond to [111]Aand [111]B, respectively.

Etched with Nakagawa solution.

Cd0.95Mn0.05Te:V (3x1016 cm-3)Cd0.95Mn0.05Te:V (6x1016 cm-3)

Defects Revealed by Chemical Etching(V-doped samples)

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Cd0.93Mn0.07T:V (3x1015 cm-3)

Annealed at 650°C for 100 hours; subsequently the temperature was lowered to 450 C and then to 250 C. (Temp. gradient ~3-5 C/cm)

Micro-twins

Improved V-doped crystals

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Contrast in the diffraction images corresponds to strains and dislocations.

Examples of diffraction topography images taken for three 2-mm thick V-doped samples

IR image WBXT image

Diffraction Topography Images of V-doped samples

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Results From In-doped Samples

In-doped CMT grown by Dr. Longxia Li is high-quality material (similar to CZT). It is ready to use for making thin, 2-3 mm, detectors. Planned further improvements:purification, optimization of growth conditions, annealing…Unfortunately, YT went out of business last fall. We have three ingots with more material inqueue for processing.

Ingot # 1 Ingot # 2 Ingot # 3

Mn concentration 5%Growth rate 0.8 mm/hour

Dopant concentration 6 ppm 4 ppm 2 ppmExtra Cd, Cd/CMT 0 2x10-4 3.3x10-4

Resistivity, ohm-cm >1010 3x1010 3x1010

Possible detector sizes <1 cm3 2x2x2 cm3 2x2x2 cm3

Twins concentration High Low LowTe inclusions concentration

~106 cm-3 ~105 cm-3 104–105 cm-3

Te inclusions size 5-20 µm 5-15 µm 3-5 µmElectron mu-tau, cm2/V 10-3 3x10-3 3x10-4

Electron mobility 500-700 cm2/V·s

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CMT Ingot grown by Yinnel Tech

Ingot # 3Diameter 2 inLength 4 in Single

crystal

Fabricate 12-mm long detectors

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Spectral responses of In-doped samples

Channels

Am-241Planar detector10x10x2 mm3

Cs-137Virtual Frisch-grid detector6x6x12 mm3 (no depth-sensing corrections)

Channels

The best measured electron mu-tau is 3x10-3 cm2/V

This value is good for early growth runs and acceptable for thin detectors

Good performance of thin detectors

Broad photopeak

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Ingot # 3 had smaller sizes and concentration of Te inclusions

1.1x1.5x6 mm3

Reconstructed Images of Size and Volumetric Concentration of Te Inclusions

Ingot # 2 Ingot # 3(has extra Cd)

Ingot # 2 Ingot # 3Total concentration, cm-3 3.4x105 9.5x104

Inclusions with >10 µm diameter 1.6x105 1.4x103

1.1x1.5x6 mm3

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Dislocations:dislocations patterns are very similar tothose seen in CZT crystals grown by YT.

Overall concentration is much less thanin the case for V-doped samples

Prismatic punching defects: the diameterof the star-shaped features is in therange of 50 µm to 500 µm, and theconcentration ~5-10 cm2.

Nakagawa-etched surface of an In-doped CMT sample

Walls of dislocations in In-doped samples

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Result Highlights

• We achieved our Phase-I goal: Demonstration of CMT detector performance approaching that of CZT detectors

• Demonstrated that In-doped CMT is much closer to its anticipated performance as radiation detectors than other alternative materials: TlBr and HgI2

– Large crystal volumes, 1010 Ω·cm, 3x10-3 cm2/V, and stable response

• Conducted material and device characterization experiments– Detectors: I-V, µe, (µτ)e, internal E fields, energy spectra, and high-resolution x-ray

response mapping data– Materials: DLTS, TCT, PL, EPDs, XRD, PCD and IR transmission

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Future work

• Test more samples to understand yields of good detectors and their properties

– Near Term: Fabricate new detectors from YTI ingots 2 and 3

• Continue to work with Polish Academy of Sciences, but seek other potential collaborators

• Use Yinnel Tech equipment to grow CMT at BNL. Investigate role of indium doping and growth conditions.

• Share the results and provide CMT to existing and new collaborators

• Conduct annealing experiments (started with CZT) under a broader range of temperatures and gas overpressures

• Establish purification and synthesis capabilities for Mn and MnTe

21

CMT Growth Facility at BNL

• We acquired two 3-in furnaces from YIT

• The furnaces are in a process of being installed

• We hired a new scientific staff member with expertise in CMT growth

• We placed a contract with Dr. Longxia Li as consultant to help us grow CMT and provide training on YIT’s equipment

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Laser Technology West wire saw can cut the crystals precisely at the rate of ~1 inch/hour.

Mechanical and chemical polishing including chemo-mechanical polishing

are available

Crystal Cutting & Polishing

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List of Publications (11)Author Title

A. Hossain, S. Babaloa, A. E. Bolotnikov, G. S. Camarda, Y. Cui, G. Yang, M. Guo, D. Kochanowska, A. Mycielski, A. Burger and R. B. James

Effects of Chemical Etching on the Surface Roughness of CdZnTe and CdMnTe Gamma-Ray Detectors, in SPIE Conference on Hard X-Ray, Gamma-Ray and Neutron Detector Physics X, Vol. 7079, edited by A. Burger, L. Franks and R. B. James (SPIE, Bellingham, WA, 2008), pp. 70791E-1. October 2008.

Y. Cui, A. E. Bolotnikov, A. Hossain, G. S. Camarda, A. Mycielski, G. Yang, D. Kochanowska, M. Witkowska-Baran, and R. B. James

CdMnTe Crystals for X-Ray and Gamma-ray Detection, in SPIE Conference on Hard X-Ray, Gamma-Ray and Neutron Detector Physics X, Vol. 7079, edited by A. Burger, L. Franks and R. B. James (SPIE, Bellingham, WA, 2008), pp. 70790N-1. October 2008.

A. Hossain, Y. Cui, A. E. Bolotnikov, G. S. Camarda, G. Yang, D. Kochanowska, M. Witkowska-Baran, A. Mycielski and R. B. James

Vanadium-Doped Cadmium Manganese Telluride Crystals as X- and Gamma-Ray Detectors, Journal of Electronic Materials, submitted Nov. 2008.

M. Witkowska-Baran, A. Mycielski, D. Kochanowska, A. J. Szadkowski, R. Jakiela, B. Witkowska, W. Kaliszek , J. Domagała, E. Łusakowska, V. Domukhovski, K. Dybko, Y. Cui and R. B. James

Good Electrical Contacts for High-Resistivity (Cd,Mn)Te Crystals, IEEE Trans. on Nuclear Science and IEEE Conference Record, submitted November 2008.

D. Kochanowska, A. Mycielski, M. Witkowska-Baran, A. Szadkowski, B. Witkowska,W. Kaliszek, Y. Cui and R. B. James

Tellurium precipitates in (Cd,Mn)Te:V crystals: Effects of annealing, IEEE Trans. on Nuclear Science and IEEE Conference Record, submitted November 2008.

K. H. Kim, G. S. Camarda, A. E. Bolotnikov, R. B. James, Jinki Hong, and SunUng Kim

Improved carrier-transport properties of passivated CdMnTe crystals, Journal of Applied Physics, 105, 093705 (2009) submitted May 2009.

A. S. Cross, J. P. Knauer, A. Mycielski, D. Kochanowska, M. Wiktowska-Baran, R. Jakieła, J. Domagała, Y. Cui, R. B. James, and Roman Sobolewski

(Cd,Mn)Te Detectors for Characterization of X-Ray Emissions Generated During Laser-Driven Fusion Experiments, IEEE Trans. On Nuclear Science (submitted)

D. M. Kochanowska, A. Mycielski, M. Witkowska-Baran, A. Szadkowski, B. Witkowska, W. Kaliszek, Y. Cui, R. B. James

Influence of Annealing on Tellurium Precipitates in (Cd,Mn)Te:V Crystals, 2008 IEEE Room-temperature Semiconductor Detectors Conference, October 23, 2008, Dresden, Germany by D. M. Kochanowska (PAS).

M. Witkowska-Baran, A. Mycielski, D. M. Kochanowska, A. J. Szadkowski, B. Witkowska, W. Kaliszek, E. Łusakowska, R. Jakieła, V. Domukhowski, K. Dybko, J. Domagała, Y. Cui, R. James,

Technique of Making Good Electrical Contracts to High-resistivity (Cd,Mn)Te Crystals, 2008 IEEE Room-temperature Semiconductor Detectors Conference, October 23, 2008, Dresden, Germany by M. Witkowska-Baran (PAS).

O.S. Babalola, A. E. Bolotnikov, M. Groza, A. Hossain, S. Egarievwe, R.B. James and A. Burger

Study of Te inclusions in CdMnTe crystals for nuclear detector applications, Journal of Crystal Growth, Accepted

G. Yang and R. James Applications of CdTe, CdZnTe, and CdMnTe Radiation Detectors, Book chapter on “Semi-Conductor Detectors” Submitted

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List of Presentations (7)Author Title

A.E. Bolotnikov, Y. Cui, G. Camarda, A. Hossain, G. Yang, and R. B. James

Development of Room-Temperature CdMnTe Gamma-Ray Detectors, RadSensing 2008, NA22 Program Review, June 18, 2008, Brookhaven National Laboratory, Upton, New York.

A. Hossain, A.E. Bolotnikov, G. Camarda, Y. Cui, G. Yang, and R. B. James

Defects in CdZnTe and CdMnTe Crystals Revealed by Etch Pit Densities and X-ray mappings, SPIE Conference on Hard X-Ray, Gamma-Ray and Neutron Detector Physics X, August 12, 2008, San Diego, CA.

Y. Cui, A. Bolotnikov, G. Camarda, G. Yang, R. James, A. Mycielski, D. Kochanowski, and Witkowska-Baran

Potential Application of (Cd,Mn)Te in X-ray and Gamma-ray Detection, SPIE Conference on Hard X-Ray, Gamma-Ray and Neutron Detector Physics X, August 12, 2008, San Diego, CA.

A. Mycielski, M. Witkowska-Baran, D. Kochanowska, A. J. Szadkowski, R. Jakieła, B. Witkowska, W. Kaliszek , J. Domagała, E. Łusakowska, V. Domukhovski, K. Dybko, Y. Cui, R. James, A. Burger, M. Groza, R. Sobolewski, A. Cross, P. Krauer

(Cd,Mn)Te as a New Material for X-Ray and Gamma-Ray Detectors, 2008 IEEE Room-Temperature Semiconductor Detectors Conference, October 23, 2008, Dresden, Germany.

Y. Cui, A. Bolotnikov, A. Hossain, G. Camarda, G. Yang and R. James

Characterization and Development of (Cd,Mn)Te Detectors, 2008 IEEE Room-Temperature Semiconductor Detectors Conference, October 23, 2008, Dresden, Germany.

A. Hossain, Y. Cui, A. Bolotnikov, G. Camarda, G. Yang, D. Kochanowska, M. Witkowska-Batan, A. Mycielski and R. James

Vanadium-Doped Cadmium Manganese Telluride (Cd1-xMnxTe) Gamma-Ray Detectors, 2008 U.S. Workshop on the Physics and Chemistry of II-VI Materials, November 12, 2008, Las Vegas, NV

Y. Cui, A. E. Bolotnikov, A. Hossain, G. S. Camarda, A. Mycielski, G. Yang, D. Kochanowska, M. Witkowska-Baran, and R. B. James,

CdMnTe in X-Ray and Gamma-ray Detection: Potential Applications, SPIE on Hard X-Ray, Gamma-Ray and Neutron Detector Physics X, San Diego, August 2008.