R. Patel

Properties of ZnO/W-doped In2O3/ZnO multilayer thin films deposited at different growth temperatures

Multilayer thin films of zinc oxide and tungsten-doped indium oxide are deposited by the pulsed laser deposition technique using a KrF excimer laser. The effect of growth temperature on the properties of multilayer films is studied. It is observed that these films are highly transparent and the transparency of the films increases with growth temperature. X-ray diffraction study reveals that films grown at high growth temperature are crystalline, while films grown at low growth temperature are amorphous in nature. The electrical properties such as conductivity and electron mobility of the multilayer films increase with growth temperature.

Investigations of dc electrical properties in electron-beam modified carbon nanotube films: single- and multiwalled

Carbon nanotubes (CNTs) in the family of nanostructured carbon materials are of great interest because of several unique physical properties. For space applications, it needs to be shown that CNTs are physically stable and structurally unaltered when subjected to irradiation becomes indispensable. The CNT films were grown by microwave Carbon nanotubes (CNTs) in the family of nanostructured carbon materials are of great interest because of several unique physical properties. For space applications, it needs to be shown that CNTs are physically stable and structurally unaltered when subjected to irradiation becomes indispensable. The CNT films were grown by microwave plasma-assisted chemical vapor deposition (MWCVD) technique using Fe as catalyst. Synthesis of both single- and multiwalled CNTs (SW and MW, respectively) were achieved by varying the thickness of the Fe catalyst layer. To investigate the influence of electron-beam irradiation, CNTs were subjected to low and/or medium energy electron-beam irradiation continuously for a few minutes to several hours. The CNT films prior to and post-irradiation were assessed in terms of their microscopic structure and physical properties to establish property-structure correlations. The characterization tools used to establish such correlations include scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), Raman spectroscopy (RS), and current versus voltage ( I-V ) measuring contact resistance ( two-probe ) and dc conductivity ( four-probe ) properties. Dramatic improvement in the I-V properties for single-walled (from semiconducting to quasi-metallic) and relatively small but systematic behavior for multi-walled (from metallic to more metallic) with increasing irradiation hours is discussed in terms of critical role of defects. Alternatively, contact resistance of single-walled nanotubes decreased by two orders of magnitude on prolonged E-beam exposures. Moreover, these findings provided onset of saturation and damage/degradation in terms of both the electron beam energy and exposure times. Furthermore, these studies apparently brought out a contrasting comparison between mixed semiconducting/metallic ( single-walled ) and metallic ( multiwalled ) nanotubes in terms of their structural modifications due to electron-beam irradiation.

Magneto-Transport Properties of Nonmagnetic Doped (Zn,Mn) O Dilute Magnetic Semiconductor

In this paper, nonmagnetic elements (Al and Cu) doping effect on the structural and magneto-transport properties of Zn0.85Mn0.15O (ZnMnO) dilute magnetic semiconductors were reported. The structural characterization was performed using XRD, Raman spectroscopy, AFM and SEM. Temperature dependent electrical resistivity, Hall effect, and were carried out using a standard magneto-transport set-up.

Effect of Substrate Variation on Electrical and Magnetic Properties of Mn Doped ZnO of Dilute Magnetic Semiconductors

In this paper, the effect of substrate on the domain structure growth and electrical and magnetic properties of epitaxial Mn-doped Zn 0.8 Mn 0.15 O ( ZnMnO ) thin films has been investigated. Epitaxial thin films of ZnMnO dilute magnetic semiconductors ( DMS ) were grown on various substrates such as single crystal sapphire, single crystal silicon, and quartz substrates using Pulsed Laser Deposition ( PLD ) technique . Structural, surface, magnetic, and optical properties have been observed on these films using X-Ray diffraction ( XRD ), Atomic Force Microscopy ( AFM ), Scanning Electron Microscopy ( SEM ), and Raman spectroscopy. X-Ray Diffraction shows that films are highly epitaxial and c-axis oriented with some induced strain. AFM images show that film surface is smooth with RMS roughness of the order of 1-2 nm over 5*5sq.micron. Magnetic characteristic properties such as carrier concentration, mobility, and temperature dependent resistivity were also investigated. Carrier concentration decreases and mobility increases for both the films on silicon and quartz substrates when compared to film on sapphire.

Nonmagnetic Doping Effect on the Magneto-Transport Properties of Mn Doped ZnO Dilute Magnetic Semiconductors

In this paper we report non magnetic elements (Al and Cu) doping effect on the structural and magneto-transport properties of Zn 0.85 Mn 0.15 O dilute magnetic semiconductors. Thin films of undoped Zn 0.85 Mn 0.15 O (ZnMnO), Al doped Zn 0.80 A l0.05 Mn 0.15 O (ZnMnAlO), and Cu doped Zn 0.85 Cu 0.05 Mn 0.15 O (ZnMnCuO) were grown on sapphire single crystals using pulse laser deposition technique. X-Ray Diffraction and Raman Spectra confirm the epitaxial growth with a strong orientation along the c-axis. Scanning Electron Microscopy and Atomic Force Microscopy reveals surface microstructure of all the films. Magneto transport properties quantify the carrier concentrations and mobilities at room temperature in all the films.