Mn doped SnO x thin films have been fabricated by extended annealing of Mn/SnO 2 bilayers at 200°°C in air for 110 h. The dopant concentration was varied by controlling the thickness of the metal layer. The overall thickness of the film was 115 nm with dopant concentration between 0 and 30 wt% of Mn. The films exhibit nanocrystalline size (10-20 nm) and presence of both SnO and SnO 2. The highest transmission observed in the films was 75% and the band gap varied between 2⋅ ⋅7 and 3⋅ ⋅4 eV. Significantly, it was observed that at a dopant concentration of ~ 4 wt% the transmission in the films reached a minimum accompanied by a decrease in the optical band gap. At the same value of dopant concentration the resistivity also reached a peak. This behaviour appears to be a consequence of valence fluctuation in Sn between the 2+ and 4+ states. The transparent conductivity behaviour fits into a model that attributes it to the presence of Sn interstitials rather than oxygen vacancies alone in the presence of Sn 2+ .

The optical properties of nanocrystalline silicon (nc-Si), formed by nickel (Ni) induced crystallization of amorphous silicon (a-Si) films, are presented. Growth of nc-Si was characterized by Raman spectroscopy and UV–vis–NIR spectrophotometry. Significantly, the onset of crystallization occurred at 600 °C within 15 min of annealing, as evidenced from the Raman peak centered at 514 cm−1. It is demonstrated that the shape of the optical absorption spectrum is a function of thickness, substrate temperature, topological disorder and metal content in the films. Ni doping of the films results in optical inhomogeneity in the films and therefore anomalous dispersion in the behavior of the refractive index. It is further shown that these parameters also influence the position of the Urbach edges. The present study shows that metal induced crystallization of a-Si does not require extended durations of annealing and that the crystallization process is accompanied by structural, chemical and microstructural inhomogeneity in the films.

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The growth of Ag nanostrucutres on borosilicate glass substrates by ion beam sputter deposition in the Ar ion energy range from 150 to 600 eV is demonstrated. Rates of deposition as low as 0.01 nm/s are achieved at an Ar ion energy of 150 eV. This leads to the formation of a random array of nearly spherical Ag particles with a mean size of approximately 100 nm, separated by distances of similar order of magnitude. The particles organize themselves into arrays over lengths of at least 10 microm. As the thickness is increased from 3 to 18 nm there is a transition in morphology from an array to linear chains and finally a dense continuous film. There is a similar microstructural evolution as a function of increasing ion energy. The plasmon resonances can be tuned depending on shape, size and interparticle distances. As the thickness of the films increase, the main plasmon peaks can be tuned from 380 to 680 nm. The spheroidal shape of the particles induces additional peaks (localized surface plasmons) centered around 430 +/- 10 nm. Detailed simulations have been carried out based on Maxwell Garnett theory to distinguish the effects of shape and size on plasmon resonances. It is demonstrated that shape rather than the size of the particles has a stronger influence on the shift in plasmon resonances.

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