Properties Of Zinc Oxide Layers Research Articles

Topographic, optical and chemical properties of zinc particle coatings deposited by means of atmospheric pressure plasma

In this research, topographic, optical and chemical properties of zinc oxide layers deposited by a cold plasma-spray process were measured. Here, zinc micro particles were fed to the afterglow of a plasma spark discharge whereas the substrates were placed in a quite cold zone of the effluent plasma jet. In this vein, almost closed layers were realised on different samples. As ascertained by laser scanning and atomic force microscopic measurements the particle size of the basic layer is in the nanometre scale. Additionally, larger particles and agglomerates were found on its top. The results indicate a partial plasma-induced diminishment of the initial particles, most probably due to melting or vaporisation. It is further shown that the plasma gives rise to an increased oxidation of such particles as confirmed by X-ray photoelectron spectroscopy. Quantitative analysis of the resulting mixed layer was performed. It is shown that the deposited layers consist of zinc oxide and elemental zinc in approximately equal shares. In addition, the layer's band gap energy was determined by spectroscopic analysis. Here, considerable UV blocking properties of the deposited layers were observed. Possible underlying effects as well as potential applications are presented.

Optical investigations of ZnO layers affected by some selected gases in the aspect of their application in optical gas sensors

Abstract The paper presents the results of investigations of zinc oxide (ZnO) layers as a potential sensing material, being affected by certain selected gaseous environments. The investigations concerned the optical transmission through thin ZnO layers in wide spectral ranges from ultraviolet to the near infrared. The effect of the gaseous environment on the optical properties of zinc oxide layers with a thickness of ~ 400 nm was analyzed applying various technologies of ZnO manufacturing. Three kinds of ZnO layers were exposed to the effect of the gaseous environment, viz.: layers with relatively slight roughness (RMS several nm), layers with a considerable surface roughness (RMS some score of nm) and layers characterized by porous ZnO structures. The investigations concerned spectral changes in the transmission properties of the ZnO layers due to the effect of such gases as: ammonia (NH3), hydrogen (H2), and nitrogen dioxide (NO2) in the atmosphere of synthetic air. The obtained results indicated the possibility of applying porous ZnO layered structures in optical gas sensors.

Preparation and Characterization of ZnO Nanocrystalline Layers

This work consists on the study of the optical properties of zinc oxide layers. These Layers are elaborated under various conditions by cathode sputtering on glass substrates and by thermal oxidations of Zn layers deposited on different types of substrates by vacuum evaporation. The oxidation treatments of Zn are made in oxygen atmosphere at temperatures between 400˚C and 450˚C for different times. The analyses by diffraction of X-rays, Optical Microscopy and Scanning electron microscopy enabled us to understand that the zinc oxide films deposited by cathode sputtering on a glass substrate and having a thickness of at least 240 nm and those prepared by thermal oxidation at 450˚C during 2 hours of layers of Zn on an alumina substrate are homogeneous and consist of grains of size 30 nm. The optical transmission measurements show that the gap is around 3.02 eV for layers obtained by oxidation and 3.3 eV for those deposited by sputtering. These samples have a good optical transparency in the visible.

Electrical and optical properties of zinc oxide layers grown by the low-temperature atomic layer deposition technique

This paper reports on the electrical and optical properties of zinc oxide thin films grown at the temperature range between 160 and 240 °C by the atomic layer deposition method using diethylzinc (Zn(C2H5)2, DEZn) and deionized water precursors. Silicon and glass were used as substrates for the ZnO growth. These films were characterized by atomic force microscopy (AFM), scanning electron microscopy (SEM), low temperature photoluminescence (LT PL) and low temperature Hall effect measurements. This analysis revealed that all the obtained as-grown ZnO layers are fairly smooth (with a roughness RMS parameter less than 4 nm), show a metallic-like conductivity, exhibited a carriers' concentration (n) of 1019–1020 cm−3 which was found to be practically independent of temperature between 7 and 300 K. From the LT PL spectra, it was established that the carriers' concentration is nearly inversely proportional to the intensity of the LT PL edge emission peak. These observations, together with the fact that the Hall mobility slightly increases at higher temperatures, indicate the existence of a competitive scattering mechanism (on grain boundaries as well as on ionized impurities). However, ionized impurity scattering seems to be the dominant factor limiting the carrier mobility in the discussed case. Moreover, the results suggest that efficient non-radiative Auger processes are responsible for the observed photoluminescence (PL) quenching in the samples with higher electron concentration.

Luminescence mechanisms of zinc oxide layers obtained by isovalent substitution

This paper discusses the luminescence properties of zinc oxide layers obtained by thermally annealing single-crystal substrates of undoped zinc selenide in air. It is established that the photoluminescence spectrum at 300K in the 1.6–3.2-ev region consists of red, green, yellow, and UV bands. The first three are caused by transitions via deep levels, while the UV band is caused by interband recombination accompanied by interaction of the carriers with LO phonons.