Crystalline SiC samples were prepared in solidification of silicon melt saturated by carbon solved from the inner wall of a graphite crucible. The crystalline structure of the samples was analysed in Raman spectroscopy and confirmed as 3C-SiC both in x-ray diffraction and x-ray photoelectron spectroscopy (XPS). The Raman spectra of the samples present a strong sharp peak located at 796.3cm-1 with a full width at half maximum about 6cm-1 and three weak peaks broadened around 1525.6, 1631.4 and 1719.1cm-1, respectively. The former belongs to the transverse optical phonons of 3C-SiC, while the latter can be attributed to the second-order scattering. However, the longitudinal optical mode of 3C SiC has not been found for our samples. An additional broadened peak at 532.2 cm-1 may imply the existence of some lattice defect in the samples, which is related to nitrogen introduced unintentionally into the lattice in the growth process and confirmed in XPS of N 1s binding energy centred at 400.9 eV.

Intense photoluminescence (PL) has been observed at room temperature from the polycrystalline Sic samples prepared from carbon-saturated Si melt at a temperature ranging from 1500 to 1650

Pb (Zr, Ti,) O, (PZT) films were prepared on the ITO coated glass plates in sol-eel dip-coating process and post-annealing at different temperatures. The structural properties of the films were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). It is shown that the PZT ferroelectric thin films with (110) preferential orientation and well-crystallized perovskite structure can be obtained after annealing at 680℃ for 30 minutes. The P-E hysteresis loops were measured by the Sawyer-Tower test system with a compensation resistor at room temperature. Values of the remanent polarization (P,) and the coercive electric field (E,) are 19.36C/em2 and 95kV/em, respectively, for the prepared PZT thin films. The relative dielectric constant c' and the dissipation factor tg• of the PZT thin films are equal to 639 and 0.23. respectively, which were measured in a LCR meter.

If a Darlington transistor is triggered by the photocurrent output from an individual photodiode, the electromagnetic interference (EMI) problem may still exist because the direct input of the Darlington is an actually electronic signal. To eliminate the EMI problem completely, we propose an absolutely light-activated Darlington transistor made of SiC, in which p-SiCGe/n-SiC heterojunction is employed to produce a base current by means of optical illumination. Performance of the novel light-activated power switch was simulated using MEDICI tools, which has shown that the light-activated device has very good switching characteristics especially for a triggering light intensity greater than 0.23 W/cm2. For a relatively weak light, the device can be switched to the ON state only for a higher bias voltage.

A novel technique has been developed to lithographically make fine patterns on PZT films. Employing chemical modification in acetylacetone (AcAc), we have obtained an UV photosensitive PZT sol from which the PZT films to be patterned can be prepared. With methanol as solvent and AcAc as chemical modifier, three sols used to compose the PZT coating sol are obtained from Zirconium oxynitrate (ZrO(NO3)2), lead acetate (Pb (CH3COO)2), and tetrabutyl titanate ((C4H9O)4Ti), respectively. By means of UV-vis and FT-IR spectrophotometers we have found that AcAc can associate with Zr, Pb, and Ti ions to form three chelate complexes, the UV absorption peaks of which are located at wavelength 304, 315 and 329 nm, respectively. However, the photosensitive PZT coating sol has UV absorption peak at around 312 nm. Both the chelate complexes in sol and the UV absorption peak can be remained in the gel films. When the photosensitive PZT gel film is irradiated by UV light containing 312 nm wavelength, its solubility in solvents such as alcohol, acetone and so on is reduced remarkably, while the UV absorption peak disappears with the dissociation of the chelate complexes correspondingly. Utilizing the characteristics, a fine pattern can be obtained by irradiation of UV light on the PZT gel film through a pattern mask and dissolving the non-irradiated area in suitable solvent. After annealing at 680