Sn-doped ZnO nanocrystalline thin films with enhanced linear and nonlinear optical properties for optoelectronic applications

Semiconductor waveguide fabrication for photonics applications is usually performed in a planar geometry. However, over the past decade a new field of semiconductor-based optical fiber devices has emerged. The drawing of soft chalcogenide semiconductor glasses together with low melting point metals allows for meters-long distributed photoconductive detectors, for example.[1,2] Crystalline unary semiconductors (e.g., Si, Ge) have been chemically deposited at high pressure into silica capillaries,[3,4] allowing the optical and electronic properties of these materials to be exploited for applications such as all-fiber optoelectronics.[5-7] In contrast to planar rib and ridge waveguides with rectilinear cross sections that generally give rise to polarization dependence, the cylindrical fiber waveguides have the advantage of a circular, polarization-independent cross section. Furthermore, the fiber pores, and thus the wires deposited in them, are exceptionally smooth[8] with extremely uniform diameter over their entire length. The high-pressure chemical vapor deposition (HPCVD) technique is simple, low cost, and flexible so that it can be modified to fill a range of capillaries with differing core dimensions, while high production rates can be obtained by parallel fabrication of multiple fibers in a single deposition. It can also be extended to fill the large number of micro- and nanoscale pores in microstructured optical fibers (MOFs), providing additional geometrical design flexibility to enhance the potential application base of the fiber devices.[9] Semiconductor fibers fabricated via HPCVD in silica pores also retain the inherent characteristics of silica fibers, including their robustness and compatibility with existing optical fiber infrastructure, thus presenting considerable advantages over fibers based on multicomponent soft glasses.

Zinc selenide optical fibers.

patterns revealed that the ZnO thin films were polycrystalline and have a wurtzite (hexagonal) structure The film crystallites are preferentially oriented with (002) planes parallel to substrate surface Some important structural parameters (lattice parameters of the hexagonal cell, crystallite size, Zn‐O bond length, residual stress, etc) of the films were determined The surface morphology of the prepared ZnO thin films, investigated by atomic force microscopy, revealed a uniform columnar structure The spectral dependence of transmission coecient has been studied in the wavelength range from 300 nm to 1700 nm The optical energy band gap calculated from the absorption spectra (supposing allowed direct band-to-band transitions) are in the range 317‐319 eV The dependence of the microstructural and optical characteristics on the preparation conditions (oxidation temperature, oxidation time, etc) of the oxidized zinc films is discussed

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M. Diciu

Papers

Structural characterization and optical properties of ZnSe thin films