Abstract
The chemical vapor deposition (CVD) process can produce single or poly-crystalline diamond samples of high purity or with controlled doping concentrations. The defect type in the CVD diamonds can be changed by heating the samples. Controlling the defect type can be used to create devices for quantum diamond switches that could be used in radiation sensors and quantum information technology. Eight samples of CVD diamonds were analyzed with Doppler broadening of positron annihilation radiation (DBAR) before and after annealing in high vacuum with an electron gun. Between temperatures of 1700 - 1850 K, nitrogen was liberated from the diamond sample. At these high temperatures, the surface was graphitized and a change in the color and transparency of the diamond was observed. Some of the samples were analyzed with DBAR during periods with and without light. The defect properties were observed to change depending on the time exposure to the positron beam and were then regenerated by exposure to light. The DBAR data is compared to photoluminescence data and a time varying defect state is discussed for detector and optical grade type II CVD diamonds.
Highlights
Much attention has been giving to chemical vapor deposition (CVD) diamonds because of their electrical and mechanical properties
For the first four samples of CVD diamonds, the heating profile was created with the aim of finding what temperature is needed for a detectable amount of nitrogen to be liberated from the sample
Our findings support Wotherspoon et al in that we see a change in the defect state with the illumination of light, we see a time decay in the Doppler broadening of positron annihilation radiation (DBAR) data when the sample is in the dark, and we report about a 2% change in the S-parameter during this light and dark switching
Summary
Much attention has been giving to CVD diamonds because of their electrical and mechanical properties. Previous work [1] [2] [3] has shown that CVD diamonds can be manipulated to tune their properties in order to create devices for quantum mechanical diamond switches that could be used in diamond sensors, io-. A majority of the work done on diamond defects has been focused on the NV center [4]-[10] while little attention was given to the divacancy [11] [12] [13] [14] [15]. During annealing, existing negatively charged monovacancy (V−) are converted to the neutral charged monovacancy (V0), the V0 migrates to, and is trapped by, any nitrogen impurities creating the NV center [19]. It is reported that prolonged annealing above 1100 K will produce the divacancy (V2) defect [14] [15]
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