Ivan Grozdanov

A solution growth route to nanocrystalline nickel oxide thin films

Abstract A chemical route for preparation of NiO thin films on glass substrates from solution containing nickel(2+) ions and urea is presented. The deposition process is based on the fact that urea decomposes to CO2 and NH3 by heating at higher temperature. The as-deposited and post-deposition heat-treated materials were characterized by X-ray analysis and FTIR spectroscopy. The results of some optical and electrical measurements made on these films are discussed. X-ray analysis confirmed that as-deposited film is 3Ni(OH)2·2H2O, while the post-deposition heat-treated one is nickel oxide with an average crystal size of 13 nm. According to the optical investigations, the absorption coefficient of the deposited material increases upon annealing, the absorption of the annealed films gradually decrease with an increase of the wavelength in the 390–820 nm region. The optical band gap for the post-deposition heat-treated films is 3.6 eV. While the as-deposited thin films are dielectric, the post-deposition treated ones are characterized by resistivity of several MΩs/cm2 at room temperature.

Fabrication and characterization of nanocrystalline cobalt oxide thin films

Abstract A simple solution growth route has been employed to synthesize nanocrystalline cobalt oxide thin films on glass substrates. The obtained films were characterized by X-ray diffraction and FTIR spectroscopy. The as-deposited films were identified as a mixture of different phases of Co(OH) 2 , while the annealed ones as Co 3 O 4. The absorption of the annealed films gradually decreases with an increase of the wavelength in the 310–820 nm region. Upon annealing, the absorption coefficient decreases. The calculated band gap energy from optical absorption data for annealed films is 2.2 eV. The as-deposited thin films are dielectric, while the post-deposition heat-treated ones are characterized by resistivity of several MΩs/cm 2 at room temperature.

A simple and low-cost technique for electroless deposition of chalcogenide thin films

A simple and economical electroless chemical deposition technique for deposition of several metal sulphides and selenides is presented. Aqueous solutions of metal salts and of sodium thiosulphate or sodium selenosulphate were used for the chemical bath. The technique is based on hydrolytic decomposition of the various metal-thiosulphate or metal-selenosulphate complexes in aqueous media, at a suitable temperature, concentration and pH. The technique presented in this paper has been successfully used for deposition of Cu2S, CuS, PbS, Sb2S3 and Sb2-xBixS3 in acidic media, and Ag2S, Cu2Se and PbSe in alkaline media, on various substrates, such as glass, metal, plastics, alumina, silicon and sapphire. Depending on the deposition time and the individual system, films of thicknesses up to 0.3 mu m were obtained from a single bath. The prospects of this technique are very good for multilayer combinations, solid solutions, and possibly ternary compounds as well. This technique was found to be suitable for any size and shape of substrate. It is a non-polluting and economical technique, since the bulk precipitates are of a relatively high purity and can be used as semiconducting powders, mineral pigments etc. The optimal conditions for deposition of each kind of film are described and the corresponding X-ray diffraction patterns are presented. Optical spectra in the wavelength interval between 300 and 2500 nm for each of the films are also supplied. The sheet resistivity and type of conductivity for each kind of film have also been determined.

Electroless chemical deposition technique for Cu2O thin films

Abstract An electroless, solution growth deposition technique for Cu 2 O thin films, suitable for large-area depositions at relatively low temperatures (⩽ 70°C) has been developed. Uniform and electroconductive Cu 2 O films were deposited on glass or clear polyester film substrates, pre-coated with an ultrathin layer of Cu x S. Post-deposition treatment of the chemically deposited Cu 2 O films in diluted solutions of Na 2 S resulted in further increase of conductivity and absorbance. Rutherford backscattering analyses confirmed sulfur implantation into the Cu 2 O films.

RAMAN SPECTRA OF THIN SOLID FILMS OF SOME METAL SULFIDES

Abstract Thin solid films of metal sulfides: Cu 2 S, CuS, PbS, Sb 2− x Bi x S 3 , Ag 2 S and HgS, and two selenides: Cu 2 Se and PbSe, were prepared by the technique of electroless chemical deposition. For the purpose of recording the Raman spectra, the metal sulfides (selenides) were deposited on glass substrates. All deposited thin films, as well as bulk samples, were characterized by the X-ray diffraction technique. The recorded Raman spectra were compared with the corresponding spectra of bulk metal sulfides (selenides) and discussed in terms of available structural data.

Chemical bath deposition of nanocrystalline (111) textured Ag2Se thin films

Abstract An inexpensive chemical bath technique for nanocrystalline Ag2Se thin films deposition on transparent polyester sheets is developed. The deposition process is essentially based on a hydrolytic decomposition of selenosulfate. The deposited films were characterized by X-ray analysis, and also optical and electrical investigations were performed. X-ray analysis of the films confirmed that the deposited material is (111) textured silver selenide, with an average crystal size of 9.2 nm. The sheet resistance of the annealed films is about 10 Ω/square, while for the as-deposited ones, it is about 20 times higher. The optical investigations show that the films exhibit gradually increasing transparency in the 320–820 nm region. Using the optical absorption data, the optical band gap for the deposited thin films was determined to be 1.8 eV. Such somewhat higher value than the previously reported ones is attributed to size quantization effects.

Chemical deposition and characterization of glassy bismuth(III) selenide thin films

Glassy thin films of bismuth(III) selenide were deposited onto glass and polyester substrates using a chemical bath deposition technique.X-Ray diffraction analysis was used for identification of the material obtained.Optical and electrical properties of the films were investigated.According to the resistance–temperature measurements, Bi Se thin films are typical semi-conducting 23 materials with calculated activation energies of 0.2 and 1.1 eV for lower and higher temperatures, respectively, and the majority charge carriers are electrons.As-deposited films are characterized with band gap energy of 2. 3 eV, which does not exhibit significant changes upon annealing. � 2002 Elsevier Science B.V. All rights reserved.

A simple solution growth technique for PbSe thin films

A low temperature (room to 70°C) chemical bath deposition technique for submicron PbSe thin films, suitable for any size and shape of substrate is reported. Uniform, mirror like films were deposited on glass or clear polyester film substrates. X-ray, optical, and electrical investigations were carried out for as-deposited as well as for annealed films.

Experimental study of the copper thiosulfate system with respect to thin-film deposition

Abstract An experimental study of the copper-thiosulfate system in mild acidic (pH ∼ 5) aqueous solutions, with respect to thin-film formation, was undertaken. Thin films of Cu x S (1 ⩽ x ⩽ 2) were deposited by a simple electroless technique on glass or transparent polyester films, at 50 °C. Thin films were deposited from chemical baths in which the ratios of copper to thiosulfate were varied from 1:1 to 1:10. Thin films of different compositions (Cu 2 S, Cu 1.8 S, Cu 1.4 S and CuS) were prepared and then characterized for morphological, optical and electrical properties. The deposited films chemically close to Cu 2 S were found to be amorphous, while the CuS films were a mixture of both amorphous and polycrystalline phases. The optical spectra of the Cu 2 S films exhibited high transmission both in the visible region of the spectrum (beyond 600 nm) and throughout the near-infrared region (800 to 2500 nm), while CuS films were found to be highly absorptive throughout the near-infrared region, with peaked transmission in the visible region at about 560 nm. The sheet resistances of the films, determined by the standard four-probe measurements, were between 100 and 650 Ω/square.

Ag and AgO thin film formation in Ag+–triethanolamine solutions

Abstract Thin film formation in aqueous Ag–triethanolamine (TEA) solutions has been studied. It was found that this bath can be used to deposit both Ag and AgO thin films on glass or polyester substrates. Uniform, specularly reflective films with thickness up to 1.2 μm were obtained from a single bath at 50°C. X-ray and some basic optical investigations were carried out for both films.