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The effects of surface preparation on CdTe-based thin film heterojunctions have been investigated through characterisation of ITO//p-CdTe and CdS/p-CdTe solar cells. The surface treatment methods include air exposure at laboratory temperature for several months, heat treatment, bromine-in-methanol etching, and bromine-in-methanol etching with subsequent hydrogen heat treatment. The authors have found that the behaviour of CdTe heterojunctions was significantly improved by the surface treatment of CdTe films exposed to air for several months at laboratory temperature prior to window material deposition. The stability of as-prepared cells has been considerably enhanced. Other methods of surface treatment seem to have insignificant effects on the improvement of subsequent heterojunctions. The explanations given for the improved performance of the solar cells are discussed.

Palladium single-crystal films have been prepared by Matthews in ultra-high vacuum by evaporation onto (001) NaCl substrates cleaved in-situ, and maintained at ∼ 350° C. Murr has also produced large-grained and single-crystal Pd films by high-rate evaporation onto (001) NaCl air-cleaved substrates at 350°C. In the present work, very large (∼ 3cm2), continuous single-crystal films of Pd have been prepared by flash evaporation onto air-cleaved (001) NaCl substrates at temperatures at or below 250°C. Evaporation rates estimated to be ≧ 2000 Å/sec, were obtained by effectively short-circuiting 1 mil tungsten evaporation boats in a self-regulating system which maintained an optimum load current of approximately 90 amperes; corresponding to a current density through the boat of ∼ 4 × 104 amperes/cm2.

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Capacitance-voltage (C-V), photoluminescence (PL) and deep level transient spectroscopy (DLTS) techniques were used to investigate deep electron states in n-type Al-doped ZnS1-xTex epilayers grown by molecular beam epitaxy (MBE). The integrated intensity of the PL spectra obtained from Al-doped ZnS0.977Te0.023 is lower than that of undoped ZnS0.977Te0.023，indicating that some of Al atoms form nonradiative deep traps. Deep level transient Fourier spectroscopy (DLTFS) spectra of the Al-doped ZnS1-xTex(x=0，0.017,0.04 and 0.046,respectively) epilayers reveal that Al doping leads to the formation of two electron traps at 0.21 and 0.39eV below the conduction band. DLTFS results suggest that in addition to the roles of Te as a component of the alloy as well as isoelectronic centers, Te is also involved in the formation of an electron trap, whose energy level relative to the conduction band decreases as Te concentration increases. Our results show that only a small fraction of Al atoms form nonradiative deep defects, indicating clearly that Al is indeed a very good donor impurity for ZnS1-xTexepilayers in the range of Te concentration studied in this work.