Boron nitride films have been deposited by a metal organic chemical vapor deposition (MO-CVD). The reaction between ammonia and triethylboron (B(C~H.0:~) is carried out in the temperature range of 750~176 with the molar ratio of NHJB(C2H.0:~ = 0-200. Colorless and transparent films are obtained at temperatures of 950~176with the molar ratio of 20-70. The composition of the films, N/B, is found to vary from 0.46 to 1.0. For a fixed NHJB(C.,H~):~, the deposition rate increases with temperature up to 1000~ and then decreases. The deposition rate shows an Arrhenius-type behavior in the temperature range of 750~176 X-ray diffraction studies indicate that the crystal structure of the films is hexagonal. The energy of the direct allowed transition, obtained from optical measurements, is estimated to be 5.90 eV.Several papers have been published describing the preparation of boron nitride films, the physical-and chemical properties, and the potential applications of those films. Boron nitride films have been prepared by chemical vapor deposition (CVD) using borontrichloride or diborane as source materials (1-3). Recently in the preparation of compound semiconductors, CVD using metalorganic compounds has been developed, and its achievements have become of major interest lately. This method, called MOCVD, has been developed with reference to the deposition of GaAs by Manasevit (4) in 1968, and a number of related papers have been reported mainly for the growth of III-V compound semiconductors (5-7).In a previous paper (8), we reported on the amorphous boron nitride films deposited by the molecular flow chemical vapor deposition (MFCVD), by which we could control the composition easily. In this paper, we report the preparation and properties of boron nitride films deposited using triethylboron and ammonia by MOCVD. ExperimentsTriethylboron (TEB, Arfa Products, 98%); ammonia (99.9%), hydrogen (99.999%), and argon (99.995%) were used to grow boron nitride films by CVD. Sapphire (12 • 12 • 0.6 mm 3) and silicon (12 x 12 • 0.25 mm 3) were used as substrates.The schematic diagram of the apparatus for the deposition of boron nitride is shown in Fig. 1. The fused quartz reaction tube has an inside diameter of 25 mm and is 600 mm long. Substrates were put on the substrate holder (sintered boron nitride) with slope of 20 ~ against the horizon and heated by external heating furnace. The substrate temperature was determined by a thermocouple attached at the rear of substrate holder.Trfethylboron was transported by bubbling hydrogen through the TEB. The temperature of the TEB saturator was controlled between 0 ~ and 25~ TEB is a colorless clear liquid, and is moisture and air sensitive and pyrohoric. The vapor pressure at 0~ is 12.5 torr (9). The flow of TEB was determined from the loss of TEB in the saturator. The preparation conditions of boron nitride films are summarized in Table I.The crystal structures of the deposited films were studied by x-ray diffraction. Optical transmission and reflection spectra of films deposited on sapph...

SUMMARYBackground: It has been reported that inhibitors of gastric acid secretion prevent bleeding after endoscopic mucosal resection for mucosal gastric neoplasm. However, uncertain whether an histamine 2 -receptor antagonist or proton-pump inhibitor is more effective. Aim: To evaluate prospectively the effectiveness of famotidine or omeprazole for ulcer management after endoscopic mucosal resection. Methods: From July 2003 to October 2004, 57 patients were randomly assigned to famotidine or omeprazole for the management of endoscopic mucosal resection. Both drugs were given intravenously for the first 2 days, thereafter by mouth. The bleeding rates after endoscopic mucosal resection, the effects on the healing of endoscopic mucosal resection-induced ulceration, and cost-benefits were compared.

We have performed photoluminescence, photoexcitation, and transmission electron microscopy measurements on boron nitride films grown by chemical vapor deposition and later reacted with potassium. After reaction, the potassium atoms were found to intercalate the BN host and to form a (2×2)R0° in-plane structure which is commensurate with the pristine BN lattice. Optical transitions with ∼2.7 eV onsets were found to occur within the ∼5-eV BN band gap and have been interpreted as Γ-point transitions between the K(4s) band and the BN(2p) bands. The absence of an appreciable shift in the E2g2 phonon frequency of the pristine and reacted films suggests that the charge transfer between the K and BN bands is very small.

Boron films of 0.1–1.5 μm thickness have been prepared on sapphire, silicon, and tantalum as substrates by the pyrolysis of decaborane false(B10H14false) in the molecular flow region (≦10−4 torr) and in a temperature range of 350°–1200°C. It is found that the deposition rate of the boron films is proportional to the decaborane partial pressure and the substrate temperature. Below 416°C, the deposition rate D is given as a function of the substrate temperature and partial pressure of decaborane. This relation isD=7.16×109·P·exp)(−39000/RTnormalswhere Tnormals is the substrate temperature, P is the pressure of decaborne, and R is the gas constant. The apparent activation energy for the decomposition of decaborane is found to be 39 kcal/mol. X‐ray and electron diffraction study indicates that the films are amorphous. The electrical conductivities vary from 3×10−5S·cm−1 at 77 K to 30 S · cm−1 at 1000 K, and the activation energy is 1.07 eV in the intrinsic temperature range (700–1000 K). The maximum value of thermo‐electric power is about 420 μV · deg−1 at 700 K, and its polarity is positive between 500 and 1000 K. The absorption coefficient, refractive index, and extinction coefficient of boron films are obtained from the measured transmittance and reflectance. The energy of the indirect allowed transition is estimated to be 1.28±0.08 normaleV .

Thin films of SrB6 were deposited on sapphire substrates using a chemical vapor deposition method, with elemental strontium and decaborane, B10H14, used as the strontium and boron sources, respectively. The formation of highly crystalline, phase-pure SrB6 films was confirmed with X-ray diffraction and reflection high energy diffraction (RHEED) analysis, and the films' thermoelectric transport properties were measured. A relatively high deposition temperature of 850 -950 °C was found to be optimal for obtaining well-crystallized films at an extremely high deposition rate. The thermoelectric transport properties of the SrB6 thin films were observed to be comparable to those reported for bulk materials, but an unexpectedly high electrical resistivity led to a reduced power factor value for the thin films.