Abstract
Crystallinity of a freestanding large (size: ~9×7mm) undoped single crystal (SC) diamond film grown by plasma chemical vapor deposition (CVD) and radiation response of a sandwich-type radiation detector made from this SC plate to α particles were investigated. The freestanding SC film was formed by elimination of a substrate using a so-called “lift-off method” after the growth of a thick-film on a pre-ion-implanted substrate. The formed SC plate has a high optical transparency, indicating no remarkable optical absorption seen in the wavelength from ultraviolet to near-infrared region. In the energy spectra of 5.486MeV α-particles, relatively sharp peaks were observed for both hole and electron transits. For the hole transit, the peak resolution of the pulse height distribution and charge collection efficiency (CCE) were ~0.7% and 98%, respectively. On the other hand, for the electron transit, the peak resolution and CCE obtained were ~4.4% and 89%, respectively. In the photoluminescence spectrum at room temperature, a strong sharp peak around 235nm corresponding to free exciton and a weak visible band mainly related to nitrogen-vacancy complex were observed. The spectral width of the (004) plane X-ray rocking curve was 16.5″. The micrograph taken using crossed-polarizers demonstrated that there are some white regions and four-petaled patterns, originating from internal strain and most likely threading dislocations, respectively.
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