Swati Ray

Properties of tin doped indium oxide thin films prepared by magnetron sputtering

Indium tin oxide (ITO) films have been prepared by the magnetron sputtering technique from a target of a mixture of In2O3 and SnO2 in the proportion 9:1 by weight. By optimizing the deposition conditions it has been possible to produce highly transparent (transmission ∼90%) and conducting (resistivity ∼10−5 Ω cm) ITO films. A resistivity ∼10−4 Ω cm has been obtained for films of thickness ∼1000 A at a comparatively low substrate temperature of 50 °C and without using oxygen in the sputtering chamber. To characterize the films, the following properties have been studied, viz., electrical conductivity, thermoelectric power, Hall effect, optical transmission, and band gap. The effect of annealing in air and vacuum on the properties of the films have also been studied.

Degradation of tin‐doped indium‐oxide film in hydrogen and argon plasma

The degradation of tin‐doped indium‐oxide (ITO) films in glow‐discharge plasmas of hydrogen and argon have been investigated. Parameters which have been varied for the study include the temperature of ITO under ion bombardment, the rf power density, the time of exposure to plasma, and the gas flow rate. After bombardment, scanning electron micrograph observation, measurement of sheet resistance, transmittance and reflectance, and Auger analysis have been carried out to decide the extent of degradation. Magnetron‐sputtered ITO films have been found to be more resistant to ion bombardment damage compared to electron‐beam evaporated films. The degradation of ITO under the plasma of the reducing species such as hydrogen has been found to take place at lower temperature and power density compared to argon plasma.

Zinc oxide—a transparent, conducting IR-reflector prepared by rf-magnetron sputtering

Al doped zinc oxide thin films with different electrical and optical properties have been developed by both non-reactive and reactive rf-magnetron sputtering in Ar and Ar+H2 atmospheres, respectively. The thin films prepared under Ar+H2 gas ambient at substrate temperatures of 100°C and 300°C show high conductivity and improved IR-reflectivity. The lowest resistivity obtained is 4.5×10−4 Ω cm at 300°C. The transmission of the ZnO : Al film in the visible range is above 90% and that at 1400 nm is only 3.2%. Most of the IR-region is thus reflected. The carrier concentration of this transparent, conducting ZnO film prepared under Ar+H2 atmosphere is 2.3×1021 cm−3. Tranmission electron micrographs reveal that the average crystallite of the sample deposited under Ar+H2 ambient is smaller compared to those prepared under Ar ambient. The 100, 002 orientations of ZnO with wurtzite structure are observed from transmission electron diffraction pattern.

Low band gap amorphous silicon deposited under He dilution in the γ regime of an rf glow discharge: properties and stability

Abstract A new type of hydrogenated amorphous silicon film having variable bandgap (1.7–1.5 eV) has been developed in an rf powered plasma enhanced chemical vapor deposition system using a mixture of silane and helium at a subtrate temperature of 210°C. The deposition conditions were chosen so that the rf glow discharge occurs in the γ regime, usually avoided because of powder formation. The influence of the chamber pressure, on the optical gap, the hydrogen content and the electronic properties is presented. Increasing the pressure up to 1.8 Torr is found to decrease the optical gap down to 1.5 eV. The densities of states of these films were measured by electron spin resonance, constant and modulated photocurrent techniques. The density of states above the Fermi level is found to be two orders of magnitude less than that of standard amorphous silicon. Moreover, unusually fast kinetics of degradation are observed. This new material could be a good alternative to amorphous silicon germanium alloys.

Characterization of tin doped indium oxide films prepared by electron beam evaporation

Abstract Tin doped indium oxide (ITO) films have been prepared by electron beam evaporation of hot pressed powder of 90% In 2 O 3 10% SnO 2 by weight. The parameters varied for optimization of film properties have been the substrate temperature and the partial pressure of the oxygen added. Properties which have been studied for characterization are the resistivity, Hall effect, transmittance and optical band gap. The structural studies have been made by X-ray diffraction and transmission electron microscopy. D.c. resistivity in the range 10 −3 −10 −4 Ω cm and visible transmittance in excess of 90% have been obtained for the films, with proper parametric adjustments. A 〈111〉 texture has been generally exhibited by the ITO films, using X-ray diffraction. This has been corroborated by electron diffraction studies.

Development of highly conductive n‐type μc‐Si:H films at low power for device applications

Highly conductive phosphorus‐doped n‐type hydrogenated microcrystalline silicon (μc‐Si:H) films have been prepared by the usual (13.56 MHz) radio‐frequency glow discharge of silane (SiH4), phosphine (PH3), and hydrogen (H2) in an ultrahigh‐vacuum deposition system. The highest conductivity of the films obtained in this study is 100 S cm−1 after optimizing the hydrogen dilution ratio, chamber pressure, substrate temperature, and doping concentration of phosphorus. The formation of microcrystallinity in the material has been studied by transmission electron microscopy, x‐ray‐diffraction studies, and Raman spectroscopy. The volume fraction of microcrystallinity in these amorphous‐microcrystalline mixed‐phase materials has been estimated from Raman spectra. Sizes of the crystallites and volume fraction of microcrystallinity vary with hydrogen dilution, chamber pressure, and substrate temperature. The variations in the properties with deposition parameters have been explained in terms of the growth kinetics. T...

Variations in structural and electrical properties of magnetron-sputtered indium tin oxide films with deposition parameters

Variations in structural and electrical properties of magnetron-sputtered indium tin oxide films with deposition parameters

Infrared vibrational spectra of hydrogenated amorphous silicon carbide thin films prepared by glow discharge

Abstract The IR vibrational spectra of a-SiC:H films prepared by rf glow discharge decompositon of a mixture of silane and methane gases have been studied. The films have been prepared under different conditions which include variation of methane concentration in the gas mixture, rf power and substrate temperature. The structures of the a-SiC:H films depend very sensitively on the deposition parameters. The spectra of p-type a-SiC:H films prepared with boron doping have also been studied. The effect of annealing on the IR spectra of the films has been investigated. Attempts have been made to analyse all these data in order to obtain information about different bonded configurations in the films.

Structural analysis of undoped microcrystalline silicon thin films deposited by PECVD technique

Undoped microcrystalline silicon thin films have been deposited by radio frequency powered plasma enhanced chemical vapour deposition technique. The structural order of silicon network in the films has been studied by Raman spectroscopy. The role of bonded hydrogen in the films and their consequences in microstructural defects have been obtained from the results of Fourier transform infrared spectroscopy. The presence of microcrystals and growth morphology of the microcrystalline films have been investigated by transmission and scanning electron microscopy, respectively. Optimized deposition conditions are obtained where properties of the microcrystalline films are suitable as absorber layer of solar cells. A highly conducting undoped microcrystalline film with 87% crystalline fraction (fc) is obtained, which exhibits columnar structure.

A study of the structural and electronic properties of magnetron sputtered tin oxide films

Tin oxide (SnOx) films have been deposited using a RF magnetron sputtering technique from a hot pressed SnO2 target in an ambient mixture of argon and oxygen. Depending on the deposition parameters the structure of the films may be varied from amorphous to crystalline along with a consequent decrease in resistivity. An attempt has been made to understand the causes of formation of insulating and conducting films. By optimizing the oxygen partial pressure and substrate temperature, SnOx films of resistivity 6.1*10-3 Omega cm with a corresponding optical transmission approximately 95% and direct optical gap of 4.13 eV can be prepared. For films having a relatively high conductivity, a long exposure to the atmosphere changed their electronic properties which could be partially recovered by annealing. The effect of annealing SnOx films in different ambients was studied.