S. Zhao

Particle‐ and photoinduced conductivity in type‐IIa diamonds

Electrical characteristics associated with radiation detection were measured on single‐crystal natural type‐IIa diamond using two techniques: charged particle‐induced conductivity and time‐resolved transient photoinduced conductivity. The two techniques complement each other: The charged particle‐induced conductivity technique measures the product of the carrier mobility μ and lifetime τ throughout the bulk of the material while the transient photoconductivity technique measures the carrier mobility and lifetime independently at the first few micrometers of the material surface. For each technique, the μτ product was determined by integration of the respective signals. The collection distance that a free carrier drifts in an electric field was extracted by each technique. As a result, a direct comparison of bulk and surface electrical properties was performed. The data from these two techniques are in agreement, indicating no difference in the electrical properties between the bulk and the surface of the ...

THICKNESS DEPENDENCE OF THE ELECTRICAL CHARACTERISTICS OF CHEMICAL VAPOR DEPOSITED DIAMOND FILMS

The electrical characteristics of chemically vapor deposited (CVD) diamond films were measured as a function of film thickness. The samples studied were polycrystalline with the average grain size increasing from approximately 1 μm on the substrate side to approximately 30 μm on the growth surface for the thickest sample. Using time‐resolved transient photoconductivity and charged‐particle induced conductivity, the collection distance (d) that a free carrier drifts under the influence of an applied electric field was measured. Our data indicate that there is a gradient in the collection distance through the material. This gradient in electrical properties has implications for electronic uses of CVD diamond.

Development of diamond radiation detectors for SSC and LHC

Abstract Diamond is a nearly ideal material for use as a radiation detector in the high rate and high radiation environments of the SSC and LHC. The recent development of the chemical vapor deposition (CVD) method of diamond growth promises to make feasible the use of diamond in large quantities. We have carried out beam tests of various samples of CVD diamond supplied by several manufacturers and have measured signals from ionizing particles. Details of these measurements are presented.

First measurements with a diamond microstrip detector

Abstract We have constructed the first high resolution strip detector using chemical vapor deposited diamond as the detection medium. Devices produced with this material have the possibility of being extremely radiation hard with direct applications at high luminosity colliders. This paper details the detector material, the low noise readout electronics and the detector module. First results from a test with high momentum charged particles in a testbeam at CERN are described. We achieved a signal-to-noise of 6:1 and an efficiency of 85% for minimum ionizing particles in the testbeam. The detector has a strip pitch of 100 μm and a strip width of 50 μm. The measured position resolution we achieved was σ = 26 μm. Future development of diamond detectors with application in particle physics experiments and other fields is discussed.

Performance of a diamond-tungsten sampling calorimeter

We report here the first measurements of a diamond-tungsten sampling calorimeter. The calorimeter consisted of twenty layers of diamond with one radiation length of tungsten per layer. The diamond layers were grown by chemical vapor deposition and were 3.0 × 3.0 cm2 wafers with an average thickness of 500 μm. We measured the energy response and resolution (σE/E) of this calorimeter in 0.5–5.0 GeV electron beams and compared the results with those from a silicon calorimeter of similar construction. Our energy resolution is σE/E = (4.7 ± 2.7)%/E≍(19.13±0.86)%/√E≍(2.3±1.8)% for the diamond-tungsten calorimeter, where ⊕ indicates addition in quadrature. This is in good agreement with our result for the silicon-tungsten calorimeter of σE/E = (3.89 ± 0.87)%/E ≍ (19.73±0.19)%/√E ≍(0.0 ± 1.6)%. We also compare our data with EGS simulations.

Diamond detectors for high energy physics

We have constructed charged particle detectors using high quality CVD diamond. We report here the measurements of a diamond-tungsten sampling calorimeter and a diamond mustrip detector. The energy response and resolution (σEE) of the calorimeter were measured using an electron beam of energy 0.5 to 5.0 GeV, and compared with those from a silicon calorimeter of similar construction. We find σEE = (4.7 ± 2.7)%/E ⊕ (19.13 ± 0.86)%/√E ⊕ (2.3 ± 1.8)% for the diamond-tungsten calorimeter, where ⊕ indicates addition in quadrature, which is in good agreement with our result of σE/E = (3.89 ± 0.87)%/E ⊕ (19.73 ± 0.19)%/√E ⊕ (0.0 ± 1.6)% for the silicon-tungsten calorimeter. The CVD diamond mustrip detector consists of 50 μm wide strips on 100 μm centers. A signal-to-noise ratio of 6: 1 and a position resolution of 25 μm was observed during recent accelerator tests.

Diamond Detectors for the SSC

Diamond is well suited as a particle detector in the high rate and high radiation environment of the SSC. The use of diamond is made possible by recent developments in the chemical vapor deposition (CVD) growth process. CVD diamonds have been studied using radioactive sources and test beams. The measured charge collection distance of CVD diamonds now exceeds that of natural diamond. No degradation of signal is observed up to a rate of 104 particles cm-2s-1. Exposure to stopping 5 MeV α particles shows no radiation damage with a dose of up to 1013 particles cm-2. Prototype diamond/tungsten and silicon/tungsten calorimeters have been constructed and tested in an electron beam at KEK. The energy resolution of the diamond/tungsten detector is comparable to the silicon/tungsten calorimeter.

Correlations Between Electrical and Material Properties of CVD Diamond

The electrical properties associated with diamond charged particle- and photo-detectors were studied using charged particle-induced conductivity (CPIC) and photo-induced conductivity (PIC). The collection distance d , the product of the excess carrier mobility μ excess carrier lifetime T and electric field E , was used to characterize the diamonds. X-ray diffraction, Raman spectroscopy, photoluminescence, SEM and TEM were performed on CVD diamond detectors to investigate the limitations of the electrical properties. Correlations were found between the electrical properties and the material characterizations.