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Title: Effects of chemo-mechanical polishing on CdZnTe X-ray and gamma-ray detectors

Here, mechanically polishing cadmium zinc telluride (CdZnTe) wafers for x-ray and gamma-ray detectors often is inadequate in removing surface defects caused by cutting them from the ingots. Fabrication-induced defects, such as surface roughness, dangling bonds, and nonstoichiometric surfaces, often are reduced through polishing and etching the surface. In our earlier studies of mechanical polishing with alumina powder, etching with hydrogen bromide in hydrogen peroxide solution, and chemomechanical polishing with bromine–methanol–ethylene glycol solution, we found that the chemomechanical polishing process produced the least surface leakage current. In this research, we focused on using two chemicals to chemomechanically polish CdZnTe wafers after mechanical polishing, viz. bromine–methanol–ethylene glycol (BME) solution, and hydrogen bromide (HBr) in a hydrogen peroxide and ethylene–glycol solution. We used x-ray photoelectron spectroscopy (XPS), current–voltage (I–V) measurements, and Am-241 spectral response measurements to characterize and compare the effects of each solution. The results show that the HBr-based solution produced lower leakage current than the BME solution. Results from using the same chemomechanical polishing solution on two samples confirmed that the surface treatment affects the measured bulk current (a combination of bulk and surface currents). XPS results indicate that the tellurium oxide to tellurium peak ratios for the mechanical polishing processmore » were reduced significantly by chemomechanical polishing using the BME solution (78.9% for Te 3d 5/2O 2 and 76.7% for Te 3d 3/2O 2) compared with the HBr-based solution (27.6% for Te 3d 5/2O 2 and 35.8% for Te 3d 3/2O 2). Spectral response measurements showed that the 59.5-keV peak of Am-241 remained under the same channel number for all three CdZnTe samples. While the BME-based solution gave a better performance of 7.15% full-width at half-maximum (FWHM) compared with 7.59% FWHM for the HBr-based solution, the latter showed a smaller variation in performance of 0.39% FWHM over 7 days compared with 0.69% for the BME-based solution.« less
 [1] ;  [2] ;  [3] ;  [1] ;  [2]
  1. Alabama A&M Univ., Normal, AL (United States); Brookhaven National Lab. (BNL), Upton, NY (United States)
  2. Brookhaven National Lab. (BNL), Upton, NY (United States)
  3. Alabama A&M Univ., Normal, AL (United States)
Publication Date:
OSTI Identifier:
Report Number(s):
Journal ID: ISSN 0361-5235; R&D Project: 20062; NN2001
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Journal of Electronic Materials
Additional Journal Information:
Journal Volume: 44; Journal Issue: 9; Journal ID: ISSN 0361-5235
Research Org:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org:
USDOE National Nuclear Security Administration (NNSA), Office of Nonproliferation and Verification Research and Development (NA-22)
Country of Publication:
United States
36 MATERIALS SCIENCE; CdZnTe; chemo-mechanical polishing; leakage current; spectral response; X-ray photoelectron spectroscopy