We have investigated transport properties of carriers excited in high-quality homoepitaxial diamond (100) films by 5.6eV photons or 15keV electrons. The high-quality single-crystalline diamond films were homoepitaxially grown on type-Ib diamond substrates at a rate of 2.5μm∕h by high-power microwave-plasma chemical-vapor-deposition (MPCVD). In cathodoluminescence (CL) measurements, strong free-exciton recombination emissions were observed at room temperature from the almost whole specimen surface, indicating the grown films have substantially high quality. It is found through an analysis of the visible emission band originating from the type-Ib substrate that decay constants estimated for excited carriers were ∼5μm in the depth direction. This is consistent with the fact that the intensity of spotlike CL images varied with an exponential function of the lateral length. From transient photocurrent measurements using ultrashort pulse laser excitations, decay times τ for the present high-quality diamond were estimated to be 15 and 100ns for electrons and holes, respectively. Charge collection distances at an electric field E of 830V∕cm were deduced to be ∼190μm and over 1.2mm for electrons and holes, respectively. The former may give a high electron drift mobility of μ∼1600cm2∕Vs while the diffusion coefficients estimated for electrons are 55±14cm2∕Vs, which is comparable with or even higher than those of Si. These physical quantities demonstrate high quality of the diamond films grown by means of the high-power MPCVD method.

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Response function measurement of layered-type chemical vapor deposition single crystal diamond radiation detectors for 14 MeV neutrons was carried out. The detector had a layered structure that was composed of a boron-doped diamond layer of 0.5 m in thickness and a nondoped diamond layer of 20 m on an inexpensive high pressure and high temperature-type Ib diamond substrate. The detector had energy resolution of 2.6% for 5.5 MeV ␣ particles. This experiment was mainly carried out in order to understand the present status of the detector as a 14 MeV neutron spectrometer and an extent of charge trapping. As result, a peak caused by the 12 C͑n , ␣ 0 ͒ 9 Be reactions was clearly observed; the best energy resolution of 6% as for a synthetic diamond radiation detector was achieved. Detection efficiency was 3.2ϫ 10 −7 counts/unit neutron fluence. However, taking the energy resolution for ␣ particles, etc., into account, the energy resolution for 14 MeV neutrons was not so high. Further improvement based on better crystal growth is indispensable.

We present herein a case of a 40-year-old male with early gallbladder cancer derived from a Rokitanski-Aschoff sinus (RAS). The patient originally presented at our hospital with epigastric discomfort, following which a diagnosis of adenomyomatosis (ADM) of the gallbladder was made, and a cholecystectomy performed. Histopathological examination of the resected specimen revealed a 7-mm well-differentiated papillo-tubular adenocarcinoma in the RAS epithelium in the body of the gallbladder. The RAS extended to the "pm" layer but the adenocarcinoma was an in situ lesion localized within the RAS epithelium. Considering the difficulties in making an early diagnosis of gallbladder cancer, active surgery should be performed for patients in whom ADM is seen in the gallbladder.

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