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Zinc sulphide nanoparticles in the size range ∼10–40 Å diameter have been synthesized using the aqueous chemical method. Scanning tunneling microscopy showed that particles are indeed nanosize particles. The size dependent band gap could be varied from a bulk value of 3.68 to 4.5 eV. X-ray diffraction indicated that nanoparticles are crystalline except for those with band gap ∼4.5±0.1 eV. Nanoparticles with particle size ∼21×2 Å diameter or energy gap 4.1×0.1 eV were doped with manganese. The photoluminescence peak at ∼600 nm corresponding to yellow light emission was observed. Atomic absorption studies show that maximum luminescence intensity is achievable with 0.12 at. wt % of Mn doping.

CdS nanoparticles exhibit size dependent optical and electrical properties. We report here the photocurrent and I–V characteristic studies of CdS nanoparticle devices. A sizable short circuit photocurrent was observed in the detection range governed by the size of the clusters. We speculate on the mechanisms leading to the photocurrent and emission in these nanometer scale systems.

The chemical and electronic aspects of a GaAs (100) surface passivated by selenium sulfide (SeS2) have been investigated by x-ray photoelectron spectroscopy and photoluminescence. It has been observed that this treatment gives rise to an arsenic selenide (As2Se3) terminated surface. No S—GaAs bonds were observed. The remarkable electronic properties and the formation of the chemically and thermally stable As2Se3 phase reveals the successful passivation. Passivation of GaAs in single step and identification of a single selenium species on the surface are considered to be the major advantages of using SeS2.

The wet chemical treatment using SeS2 is an inexpensive and simple method of depositing selenium on GaAs surfaces. This treatment improves the electronic properties of the surface as seen from the increase in photoluminescence intensity. We present our results on surface structural investigations of GaAs(110) surface passivated by SeS2 treatment using atomic force microscopy. Our results show that SeS2 treatment can passivate the GaAs(110) surface forming ordered overlayers on it.