Resonant tunneling in multiple-barrier structures with arbitrary potential profile is studied theoretically. Analytical expressions of the transmission coefficient and the resonance condition are derived by taking into account the mass difference between well and barrier layers. The basic barrier unit in the periodic multiple-barrier structure may be a compound-barrier structure, and the simplest compound-barrier unit is the double-barrier unit. Two independent resonance conditions exist in the multiple-barrier structures with compound-barrier unit and both the subband gap energy and the energy value at the center of the subband gap may be determined analytically and independently for the multiple-barrier structure with doublebarrier unit.

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

A new design of power supply based on the idea of switched capacitors, as applied to pocket computer systems, is presented. This new type of power supply is inductorless and, consequently, suitable for hybridization and even monolithic integration. The new design is also based on distinguishing characteristics of pocket digital computer systems, in which a switched-capacitor converter can work well, since minimal regulation is required. The new device may enable the pocket computer system to be powered by only one battery, resulting in a simple topology. Two switched-capacitor converters, +12 V/-12 V, +5 V and +5 V/+12 V, -12 V, are shown, respectively, as an example for demonstrating the basic principle and its performance. PSPICE simulation and laboratory models show good results for this new type of power supply.

Intense photoluminescence (PL) from porous-like SiC has been observed at room temperature. The samples were prepared by electrochemical anodization from nanocrystalline SiC thin films grown on Si (100) substrates in hot filament chemical vapor deposition. It has been found that a light-induced enhancement of the PL intensity will take place if the incident light beam from an He-Cd laser (325nm, 10mW) is employed for the excitation. Blue-shift of the PL peak energy from about 1.9 eV of as-anodized samples to about 2.1 eV and an accompanied spectral widening have also been observed for a long enough irradiation time. However, the novel effects have not been observed at low temperature. Origin of the light-induced change is suggested to be related to some light-induced metastable defects.

A theoretical analysis has been carried out to compare the resonance condition in the asymmetric double-barrier structure with that in the symmetric triple-barrier one. It is. found that. the triple-barrier structure may be considered as two quasidouble-barrier structures whose resonance condition may decide the resonance levels in the triple-barrier structure. It is confirmed that two modes exist in the triple-barrier structure: one is "normal mode consisting of doublet and the other is degenerated mode of singlet. The critical condition between the two modes is given and its physical meaning is examined. Moreover, it is confirmed that both the normal mode and the degenerated mode exist also in symmetric n-fold barrier structures (n≥3).