We have studied quantum statistical properties in a zero-temperature two-species Bose{Einstein condensate system in the presence of the nonlinear self-interaction of each species, the interspecies nonlinear interaction, and the Josephson-like tunneling interaction. It is found that the two condensates may periodically exhibit sub-Poissonian distribution. It is revealed that the correlation be t ween the two condensates can benonclassical, which means that there exists a violation of Cauchy{Schwartz inequality. The nonclassical e ect about the correlation be t ween the two condensates can berealized experimentally by properly preparing the total numbe rof atoms in the two condensates.

No abstract

No abstract

Erosion and changes in the sidewall smoothness d masking layers commonty used as dry etch masks for iil-V semiconductors have been studied for U?-, F2-and CHa/HZ-based discharges. A panicular problem with photoresist masks is the introduction of sidewall roughness which i s transferred into the underlying dielectric or semiconductor. Distortion of the resist mask also occurs during high DC bias dry etching, leading to feature widths wider than the original mask dimension. Both d these phenomena are minimized with the use d low (-100 V DC) seif-bias during the etching. Dielectric layers such as SiOl display erosion and faceting d the mask edges during extended high-bias dry etching and for small (< 1 pm) feature widths this can lead to trenching at the base of the sidewalls. Metal-based (AI, TilAu) masks are much more resistant to erosion and appear to be favoured when etching deep (> 2 pm) features into both GaAs and InP Anenide and Relared Compounds 1985 (Inst. Phys. Cant Sec 79) ed M Fujimoto (Bristol: Institute of Physics) p 367 Vodjani N and Parrens P 1987 1. V a c Sci Technol. B 5 Katz A, Pearton S J and Geva M 1990 J. AppL PiIys. 68 3110 Katz A, Pearton S J and Geva M 1991 AppL P / y s Lett. 59 286

Our study is designed to test whether or not existing 'charge transfer to the continuum' theory adequately explains the production of ci 2 U, electrons resulting from 0.2-0,s MeV H C and H: ion bombardment of thin carbon foils; the work suggests that it does not. The differential energy and angular distributions of the emitted electrons are discussed in terms of the vectorial electron-ion velocity differences (U, -vi). Although the cusp shaped peaks in both angle and energy are observed, (i) the /U, -~'~1 -l dependence predicted by all 'charge transfer into the continuum' theories is not found; furthermore, (ii) the predicted increase in cusp width when plotted in terms of (uea,) and as a function of E, is not found; finally (iii) it is confirmed that the yield of U, = ui electrons from H + bombardment is not the predicted E r 5 but rather very nearly an E,dependence through our energy range. Furthermore, the cusp widths associated with H + ions are considerably larger than those for equal velocity H i ions. Many of our observations may reflect solid state processes which occur prior to the time the ion passes through the foil surface into the vacuum.