F.J. Schmitte

Bio: F.J. Schmitte is an academic researcher from RWTH Aachen University. The author has contributed to research in topics: Thin film & Doping. The author has an hindex of 3, co-authored 3 publications receiving 170 citations.

Preparation and growth of SnO2 thin films and their optical and electrical properties

Abstract: SnO 2 films for heat-reflecting purposes are prepared on borosilicate glass by the hot spray technique from an aerosol of SnCl 4 in butyl acetate doped with fluorine. Carrier densities of up to 6 × 10 20 cm −3 and mobilities in the range 10–40 cm 2 V −1 s −1 are achieved depending on the preparation methods and conditions. From the optical spectra the dielectric function and the dynamic resistivity are determined. The frequency dependence of the resistivity above the plasma edge shows that scattering by ionized impurities and neutral defects occurs.

Transparent heat-reflecting coatings for solar applications based on highly doped tin oxide and indium oxide

Abstract: The electrical and optical properties of thin films of the highly doped oxides of In and Sn are investigated. Maximum free electron densities of 15 × 10 20 cm −3 in In 2 O 3 and 7 × 10 20 cm −3 in SnO 2 are obtained in films prepared by the hot spray technique by appropriate doping. Free electron density and mobility are strongly influenced by additional oxygen. The free electron mobility is limited mainly by ionized impurity scattering. Optimized filters are designed for solar collector and window applications, taking into account a modified Drude behaviour.

Transparent Heat Reflecting Coatings (THRC) Based On Highly Doped Tin Oxide And Indium Oxide

Abstract: A number of highly doped oxides - in particular Sn02 and In203 - have been reported to show high infrared reflectivity while being transparent to visible radiation. Their optical behaviour is based on metal-like properties i.e. high concentration and mobility of the conduction electrons and a semiconductor bandgap of about 3 eV or higher. Thin films of these oxides can be adapted for many applications and a few examples will be described. The performance of these filters strongly depends on the doping and preparation conditions. Coatings prepared by spray pyrolysis show excellent electrical and optical properties, the upper limits of which are being discussed on the basis of defect mechanisms in solids.© (1982) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Transparent conductors—A status review

Abstract: Non-stoichiometric and doped films of oxides of tin, indium, cadmium, zinc and their various alloys, deposited by numerous techniques, exhibit high transmittance in the visible spectral region, high reflectance in the IR region and nearly metallic conductivity. The electrical as well as the optical properties of these unusual materials can be tailored by controlling the deposition parameters. These transparent conductors have found major applications in a vast number of active and passive electronic and opto-electronic devices ranging from aircraft window heaters to charge-coupled imaging devices. In this status review we present a comprehensive and up-to-date description of the deposition techniques, electro-optical properties, solid state physics of the electron transport and optical effects and some applications of these transparent conductors.

Evaporated Sn‐doped In2O3 films: Basic optical properties and applications to energy‐efficient windows

Abstract: We review work on In2O3:Sn films prepared by reactive e‐beam evaporation of In2O3 with up to 9 mol % SnO2 onto heated glass. These films have excellent spectrally selective properties when the deposition rate is ∼0.2 nm/s, the substrate temperature is ≳150 °C, and the oxygen pressure is ∼5×10−4 Torr. Optimized coatings have crystallite dimensions ≳50 nm and a C‐type rare‐earth oxide structure. We cover electromagnetic properties as recorded by spectrophotometry in the 0.2–50‐μm range, by X‐band microwave reflectance, and by dc electrical measurements. Hall‐effect data are included. An increase of the Sn content is shown to have several important effects: the semiconductor band gap is shifted towards the ultraviolet, the luminous transmittance remains high, the infrared reflectance increases to a high value beyond a certain wavelength which shifts towards the visible, phonon‐induced infrared absorption bands vanish, the microwave reflectance goes up, and the dc resisitivity drops to ∼2×10−4 Ω cm. The corre...

Versatility of chemical spray pyrolysis technique

Abstract: The chemical spray pyrolysis technique (SPT) has been, during last three decades, one of the major techniques to deposit a wide variety of materials in thin film form. The prime requisite for obtaining good quality thin film is the optimisation of preparative conditions viz. substrate temperature, spray rate, concentration of solution etc. However, in recent years an emphasis has been given to a variety of atomization techniques such as ultrasonic nebulisation, improved spray hydrolysis, corona spray pyrolysis, electrostatic spray pyrolysis and microprocessor based spray pyrolysis. This is the most critical parameter as it enables control over the size of the droplets and their distribution over the preheated substrates. The enhancement in deposition efficiency and improvement in quality of the thin films can be achieved with these atomization techniques. The detailed processes are discussed in this review. An extensive review of thin film materials prepared during the last 10 years is given to demonstrate the versatility of the chemical SPT. The various conditions to obtain thin films of metal oxide, metallic spinel oxides, binary, ternary and quaternary chalcogenides and superconducting oxides are also given. The effects of precursor, dopants, substrate temperature, post annealing treatments, solution concentration etc., on the physico-chemical properties of these films are given as well. It is observed that the properties of thin films depend very much on the preparative conditions. The properties of the thin film can be easily tailored by adjusting or optimising these conditions, which in turn are suitable for a particular application.

Optical properties of sputter-deposited ZnO:Al thin films

Abstract: ZnO:Al coatings were prepared by rf magnetron sputtering of ZnO together with dc magnetron sputtering of Al onto rapidly revolving unheated substrates under weakly oxidizing conditions. Optimized films had ∼1% luminous absorptance, ∼85% thermal infrared reflectance, and ∼5×10−4 Ω cm electrical resistivity at a thickness of ∼0.3 μm. The Al content was ≲2 at. %, as determined by Rutherford backscattering spectrometry. Transmission electron microscopy and electron diffraction showed ∼50‐nm average crystallite size and a hexagonal wurtzite structure. Spectrophotometric transmittance and reflectance were recorded in the 0.2–50‐μm wavelength interval, and the complex dielectric function was evaluated by computation. The optical data were explained from an effective mass model for n‐doped semiconductors. The Al atoms are singly ionized, and the associated electrons occupy the bottom of the conduction band as free‐electron gas. The Al ions act as pointlike Coulomb scatterers and are screened by the electrons acco...

Semiconducting transparent thin films: their properties and applications

Abstract: The present state of the art of transparent, electrically conducting films, with special reference to In2O3, SnO2 and Cd2SnO4, has been reviewed. Various production techniques currently in use, and typical parameters used in the processes have been discussed in detail. Electrical and optical properties of these films have been reported as a function of various parameters, e.g. substrate temperature, doping, oxygen pressure, etc. Finally, the applications of these films in research and industry have been discussed in detail.