Metodija Najdoski

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.

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.

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.

Oriented cadmium oxide thin solid films

A chemical bath deposition technique has been developed for the preparation of Cd(O2)0.88(OH)0.24 thin films on glass and quartz substrates from alkaline media at room temperature. These films were then annealed at 473 K in order to obtain cadmium oxide films. Two baths were used for film preparation. X-Ray diffraction analysis clearly showed that the CdO films obtained from a bath without KBr have a preferred crystalline orientation in the 〈200〉 direction while those obtained from a bath containing KBr had only slightly preferred crystalline orientation in the 〈111〉 direction. The optical bandgap, Eg, was evaluated from the VIS absorption spectra. It was found that Eg for the films oriented in the 〈200〉 direction is 2.63 eV, while it is 2.57 eV for those with the slight 〈111〉orientation. The different values of the cross-over terminal points of absorption and transmittance spectra confirm the difference between the films with different crystalline orientation.

A simple chemical method for preparation of hydroxyapatite coatings on Ti6Al4V substrate

A novel, simple and economical chemical bath method for deposition of calcium hydroxyapatite coating has been developed. The coatings were prepared from EDTA solutions in alkaline media on Ti6Al4V substrates. The method is based on thermal dissociation of the Ca(EDTA)2- complex at 65–95 °C. Two chemical baths with and without presence of Na+ and Cl- were used for the deposition. The Rutherford back scattering study shows that the coating material from bath which contained sodium and chlorine ions have their presence in the coated material. The bath which has been prepared with potassium substituting sodium and nitrate substituting chlorine produced coatings with better stoichiometry, with Ca/P=1,67. The X-ray analysis revealed that the calcium hydroxyapatite coatings have preferred crystal orientation in the 002 direction.

Chemical bath deposition of mercury(II) sulfide thin layers

Thin layers of mercury(ii) sulfide have been prepared by a newly developed chemical bath deposition technique. The layers were grown on glass substrates previously coated with a very thin layer of lead sulfide (thickness <10 nm). The deposition was performed in alkaline media at 65 °C from thiosulfate complexes of mercury. X-Ray investigation indicates that the deposited material is a mercury(ii) sulfide mixture of two phases, α-HgS and γ-HgS, with α-HgS dominant. The optical bandgap,Eg, was evaluated from VIS absorption spectra and found to have a value of 3.1 eV.

Chemical solution method for fabrication of nanocrystalline iron(III) oxide thin films

A chemical solution technique for preparation of nanocrystalline iron(III) oxide thin films is developed. The deposition process is essentially based on the thermal decomposition of urea. The as-deposited and post-deposition heat-treated materials were characterized by X-ray analysis and Fourier transform infrared (FTIR) spectroscopy. Basic optical and electrical investigations were also performed. X-ray analysis confirmed that post-deposition heat-treated material is nontextured α-iron(III) oxide, with an average crystal size of 22 nm. The optical investigations show that the absorption of films (as-deposited and post-deposition treated) gradually decreases with an increase of the wavelength in the 390–820 nm region. The optical band gap for the as-deposited and post-deposition heat-treated films was determined to be 3.2 eV and 2.0 eV, respectively. The obtained α-Fe2O3 thin films exhibit a rather high resistivity at room temperature. However, our preliminary qualitative investigations have shown that the room temperature resistivity of α-Fe2O3 thin films is highly sensitive to moisture, indicating their potential applicability in moisture sensing systems.

Optical properties of thin solid films of lead sulfide

Abstract The technique of electroless chemical deposition was used for preparation of thin solid films of lead sulfide (PbS). The thin solid PbS films were deposited on a glass substrate previously coated with a very thin layer of Cu 2 S. The optimal temperature of deposition was between 343 and 363 K. The thickness of these films was controlled by changing the concentration of the reaction solutions and the deposition time. The optical properties of these thin solid films of different thickness were determined by means of near infrared spectroscopy, Raman spectroscopy and visible spectroscopy.