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The present paper deals with the study of photoluminescence (PL) and the other physical properties (structural, electrical and optical) of SnO2 thin films with controlled disorder and intrinsic defects induced during the reactive magnetron sputtering by changing oxygen flow rate from 12 to 16 sccm. The changes in unit cell volume, near band-edge optical transparency and width of Urbach tail in the films are correlated with the structural disorder and presence of intrinsic defects induced by growth under different oxygen partial pressures. The increased intensity of the PL near UV emission and decrease in the intensity of visible emission peaks with increase in oxygen flow rate is linked with the decrease in oxygen vacancies and tin interstitials in the films. With increasing oxygen content, whereas the electrical resistivity of the films minimizes to a value of 4.3 × 10−2 ohm cm at 14 sccm, the mobility of the films increases to a saturation value 15 cm2 V−1 s−1. The donor-defect concentration linked carrier density is observed to decrease monotonically from 2 × 1019 to 0.6 × 1019 cm−3.

This paper reports the charge transport mechanism at low temperatures in (110) oriented polycrystalline tin oxide (SnO 2 ) films of less than 100 nm thickness prepared by reactive sputtering in the substrate temperature (T S ) range of 350–450 °C. Undoped tin oxide films with high electrical conductivity of 11 Ω –1 cm –1 have been achieved at 350 °C. The Hall mobility increases from 6.7 to 13.9 cm 2 /V·s and carrier concentration decreases from 11 × 10 18 to 0.9 × 10 18 cm –3 as T S is increased. In the 300–100 K temperature range we found two types of conduction mechanisms: thermally activated conduction till 160 K and nearest-neighbour-hopping conduction below 160 K. At temperatures below 90 K, the Mott variable-range-hopping (VRH) conduction governs the charge transport. In all the three regimes the activation energies of conduction increase with an increase in T S , being 15–50, 0.2–9, and 2–6 meV respectively, consistent with a decrease in oxygen vacancies at higher T S . The analysis of the data in Mott VRH conduction regime suggests a systematic localization of the oxygen vacancy states with an increase in growth temperature. Even at 70 nm thickness the films behave as three dimensional with regard to the Mott VRH conduction process.

Observation of room temperature ferromagnetism (RTFM) in nano-crystalline Co-incorporated titanium dioxide [Ti(1-x)Co(x)O2(x = 0.05)] thin films prepared by spray pyrolysis technique is reported. While only the anatase phase was detected in as-deposited 5 at.% Co-incorporated TiO2 film, a small amount of rutile phase developed following its vacuum annealing. Besides, no X-ray diffraction peak corresponding to cobalt metal could be detected in any of the two films. SQUID magnetometry of both pristine and Co-doped thin films at room temperature elucidated distinct ferromagnetic behavior in 5 at.% Co-incorporated as-deposited film with saturation moment M(s) approximately 5.6 emu/cm3 which got enhanced up to 11.8 emu/cm3 on subsequent vacuum annealing. From the zero field cooled magnetization measurement we confirmed the absence of Co-metal clusters. The electrical resistivity was found to be greater than 108 omega-cm for the films. Based on the magnetic and electrical measurements the origin of RTFM has been attributed to the bound magnetic polaron (BMP) model.

Thin films and nanowires of Fe3O4 have potentiostatically been electrodeposited on ITO coated glass and employing templates in a conventional three-electrode cell using two different baths. Appropriate potential windows, suitable for films and nanowires, were estimated from cyclic voltametry. Structural property of Fe3O4 films was studied by X-ray diffraction. A large (−3.35%, at 2.3 kOe) longitudinal magnetoresistance (MR) was observed at room temperature, and the shape of MR curves showed a reduced hysteresis loop for Fe3O4 films with low coercivity. Room-temperature magnetic properties of Fe3O4 films were studied by vibrating sample magnetometer (VSM). Surface morphology of nanowires was studied by scanning electron microscope (SEM). The nonlinear I–V characteristic of nanowires was observed at room temperature. An attempt has been made to understand the conduction mechanism.

Room-temperature ferromagnetism has been observed in Co- or Mn-doped SnO 2 and Co- and F-co-doped SnO 2 thin films. A maximum magnetic moment of 0.80 μ B /Co ion has been observed for Sn 0.90 Co 0.10 O 1.925− δ F 0.075 thin films, whereas in the case of Sn 1− x Mn x O 2− δ it was 0.18 μ B /Mn ion for x =0.10. The magnetization of both Sn 1− x Co x O 2− δ and Sn 1− x Co x O 2− y − δ F y thin films depends on the free carrier concentration. An anomalous Hall effect has been observed in the case of Co-doped SnO 2 films. However, the same was not observed in the case of Mn-doped SnO 2 thin films. Carrier-mediated interaction is convincingly proved to be the cause of ferromagnetism in the case of Co:SnO 2 . It is, however, proposed that no carrier-mediated interaction exists in the case of Mn:SnO 2 . Present studies indicate that dopants and hence electronic cloud–lattice interaction plays an important role in inducing ferromagnetism.

In the present paper, the preliminary investigations of a series of ZnO thin films co-doped with indium and cobalt with an objective to elucidate the correlation, if any, between the carrier concentration and the induced room temperature ferromagnetism (RTFM), are presented. The single-phasic (Zn 99.5 In 0.5 ) 1− x Co x O thin films are deposited by spray pyrolysis. The substitution of Zn 2+ by Co 2+ has been established by optical transmission analysis of these films. The films are ferromagnetic at room temperature; and the magnetization has higher value for indium and cobalt co-doped thin film as compared with Zn0 90 Co 0.1 O thin film (having no indium).

Thin films of lithium ferrite (with general composition Li0.5Fe2.5O4) were fabricated at low temperatures (up to 650 °C) by citrate-route using spin-deposition technique. Deposited films consisted of nanometer-sized grains as evidenced by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques. XRD patterns for annealed films showed broad peaks exhibiting a spinel phase. Size of nanocrystallites is estimated to be 3–7 nm using Scherrer's equation. Average grain size ∼8.5 nm is observed from TEM images of films annealed at 650 °C. Scanning electron micrographs show the formation of spherical aggregates of around 130 nm in diameter. The AFM analysis clearly evidenced the development of nanograins even at low (∼500 °C) annealing temperatures. Significant decrease in complex dielectric permittivity (∈′ − j∈″) with frequency is observed in the low frequency (100 Hz–1 MHz) as well as in X-band microwave frequency (8–12 GHz) region. ∈′ is found to be in the range of 15.7–33.9 in low frequency region, whereas in X-band microwave frequency region, it is found to lie between 3.9 and 4.9. Similarly, ∈″ is found to be 0.16–5.9 in the low frequency region, and 0.002–0.024 in the X-band microwave frequency region. Room temperature dc resistivity of these films is estimated to lie in the range of 106–108 Ω cm. These results strongly suggest that citrate-route processed nanocrystalline lithium ferrite thin films are promising candidates for monolithic microwave integrated circuits (MMICs).

Nanocrystalline nickel ferrite and zinc doped nickel ferrite thin films with general composition Ni 1− x Zn x Fe 2 O 4 ; x =0.0, 0.2 and 0.5 were fabricated by the spin-deposition technique. Citrate precursor method was adopted to prepare coating solution used for film deposition. This method resulted in single phase, transparent, homogeneous and crack-free nanocrystalline ferrite thin films at annealing temperature as low as 400 °C. The substrates used for film deposition were ITO-coated 7059 glass, fused quartz and Si (1 0 0). The thickness of films was found to be in the range ∼1000–5500 A. The surface microstructure and morphology investigated by atomic force microscopy (AFM) confirmed the grain size of nickel–zinc ferrite films to be in nanometer range indicating nanocrystalline nature of the films. Dielectric properties such as the real (∈′) and imaginary parts (∈″) of complex permittivity were measured in the X-band microwave frequency region (8–12 GHz) by employing extended cavity perturbation technique. The M – H hysteresis measurements on the films annealed at 650 °C revealed narrow hysteresis curves with H c and M s varying for different compositions.

Alloy thin films of ternary system Co – Ni – Fe and binary systems Co – Fe , Co – Ni and Ni – Fe consisting of ~50 nm grains have been deposited by a simple and industrially viable technique of electrodeposition in galvanostatic mode on ITO-coated glass. Bath composition and current density have been varied to prepare films of different compositions and thus, in turn, obtain suitable composition for better magnetic properties. Further, an attempt has been made to deposit films in the presence of Mg 2+ in the bath and to study its linkage with the magnetic properties, i.e., saturation magnetic flux density, BS, and coercivity, HC. Our results clearly demonstrate that addition of Mg 2+ ions in the bath helps in increasing the BS considerably.

Co/Cu multilayers were electrodeposited in potentiostatic mode, using two different sulphate baths, one without any additive and other containing trisodium citrate. Deposition parameters, like deposition potential and deposition time, were established for both the baths by carrying out a series of cyclic voltammetry and chronoamperometric experiments. Thin films, having 2–20 bilayers, were electrodeposited under the established parameters. It was observed that films deposited from bath containing trisodium citrate were comparatively much smoother than films deposited from additive free bath. The films with 20 bilayers, deposited from additive free bath, exhibited a room temperature magnetoresistance of 1.5% at 9 kG, whereas magnetoresistance value enhanced to up to 5.6% at 9 kG for films deposited from trisodium citrate bath for same number of bilayers.

Nanocrystalline nickel–zinc ferrite thin films with the general formula Ni 1− x Zn x Fe 2 O 4 , where x =0.0, 0.2, 0.4 and 0.6 were fabricated via a chemical route known as the citrate precursor route. These films were spin-deposited on indium–tin oxide coated glass, fused quartz and amorphous Si-wafer substrates, and annealed at various temperatures up to 650 °C. The films annealed below 400 °C were found to be X-ray amorphous, while the films annealed at and above 400 °C were polycrystalline exhibiting a single-phase spinel structure. The average grain size of the films evaluated by transmission electron microscopy, is found to be in the range 4–8.5 nm. The room temperature DC resistivity of the films is in the range 10 3 –10 7 Ω m. Dielectric constant and dielectric loss were measured in the frequency range 100 Hz–1 MHz. Dielectric constant of the films is found to lie between 25 and 44, while the loss factor is if the order of 10 −2 . The higher values of the dielectric constant for films having higher zinc concentration are attributable to the enhanced hopping between Fe 2+ and Fe 3+ ions in these samples. The M–H hysteresis measurement of the nickel ferrite thin films annealed at 650 °C showed narrow hysteresis loop—a characteristic of soft ferromagnetic material.

Thin films of Cu–Co have been electrochemically deposited onto Cu-coated alumina substrates in a single sulfate bath. Electrochemical process parameters are expected to influence the chemical composition and microstructure and hence, physical properties of the films. We have attempted to study and understand the effect of various electrochemical process parameters like bath composition, bath temperature, deposition current density and pH of the electrolyte, along with annealing temperature and time on the magnitude of GMR in Cu–Co films. The maximization of GMR is understood in terms of an optimum distribution of the size and the separation of the magnetic particles via the thermally-induced phase segregation.

Epitaxial thin films of YBa 2 Cu 3 O 7– δ (YBCO) have successfully been grown by reactive RF-magnetron sputtering technique at a low pressure (0.95 mTorr) with T C ( R =0)=85.3 K and J C mag (4.2 K)≈2×10 7 A/cm 2 . The incorporation of oxygen in the as-grown films has been controlled by using different ambient—oxygen, air and argon—during in situ cooling. The superconducting behavior of the resulting films was studied using resistance–temperature and low field a.c.-susceptibility measurements and correlated with their structure. All the films exhibited metallic conduction in the normal state. The oxygen- and air-cooled films were superconducting, and exhibited usual orthorhombic structure, but the argon-cooled films were non-superconducting and possessed tetragonal structure. This implied that the structure of the film during deposition is tetragonal, and transforms to either of the oxygen rich orthorhombic-I or -II phases depending upon the oxygen/air ambient. The ‘ δ ’ values of 0.14, 0.32 and 0.70 and higher ‘ c ’-parameters of 1.1785, 1.180 and 1.183 nm have been obtained for oxygen-, air- and argon-cooled films, respectively.

In-situ superconducting c-axis oriented YBa2Cu307_s (YBCO) thin films have been grown at T sub = 775 °C on SrTiO3(100) and MgO(lOO) by r.f.-magnetro n sputtering at an oxygen partial pressure, which not only lies below the stability line but is more than an order of magnitude lower than its empirically suggested limit. The effect of variation in partial pressure of oxygen (POl) on the film characteristics is analyzed by employing a.c.-magnetic susceptibility, resistance-temperature variation, Rutherford backscattering, atomic force microscopy (AFM), scanning electron microscopy and X-ray diffraction techniques. The oxygen deficiency, 5, is calculated employing a number of techniques. The higher c-axis lattice parameters of the films are supportive of antisite disorder in the cations. The AFM investigations have established that Stranski-Krastanov-type growth mechanism is operative in the present case. The variation in critical current density (J™g(T)) with temperature is reported for the first time in the low pressure sputtered films exhibiting a J craas(43 K) of «4.6X 106 A cm" 2.

Thin films of amorphous (a-) Ge20Se80 − xBix (x = 4,10) and a-As2Se3 − xBix (x = 0.2, 0.5) have been prepared by thermal evaporation and characterized for their electrical and optical properties. The addition of bismuth, in excess of 4 at.%, to p-type a-Ge20Se80 and a-As2Se3 films results in large (several orders of magnitude) changes in the electrical conductivity and conversion of the conductivity from p to n type. A correlation of the electrical and optical data of the modified films suggests that the addition of bismuth causes a Fermi level shift and the electrical transport is predominantly due to hopping of electrons after being excited into localized states the conduction band edge.

Amorphous silicon-germanium (a-Si 1− x Ge x ) thin films have been prepared co-sputtering a composite target of high purity crystalline silicon (c-Si) and c-Ge using ion beam sputtering technique. The desired composition has been obtained by suitably adjusting the exposed areas of c-Si and c-Ge. The electrical, optical and structural properties of these films have been investigated as functions of composition (for a-Si 1- x Ge x ) and ion beam energy-voltage and substrate temperature (for a-Si 50 Ge 50 ). The amorphous silicon-germanium films deposited with increased x or decreased beam voltage and/or substrate temperature, in general, exhibit an increase in their electrical conductivity. The conduction mechanism associated with these films is dominated by hopping between the localized states. The a-Si 50 Ge 50 films deposited at a beam energy of 1000 V and substrate temperature of 300°C have a band gap and an electrical conductivity of 1.1 eV and 3 × 10 −5 (Ωcm) -1 respectively.

Infrared and spectroscopic ellipsometric studies have been done on thin films of hydrogenated amorphous silicon (a-Si:H), germanium (a-Ge:H) and silicongermanium alloy of a typical composition (a-Si28Ge72:H) prepared by reactive ion beam sputtering (RIBS). Films deposited at increasing H2:Ar flow ratio generally show enhanced dihydride and polyhydride bonding and a decreased value of e2max. A correlation of the two results reveals that the increase in hydrogen content affects the growth process considerably and makes the films density deficient and inhomogeneous by increasing the volume fraction of voids, network strains and vacancies. The a-Si28Ge72:H films deposited at increasing H2:Ar flow ratio show a preferential attachment of hydrogen to silicon rather than to germanium. It has been found that RIBS-prepared films are more density deficient as compared to films deposited by glow discharge, owing mainly to the presence of dihydride species.

Electrodeposition has emerged as a novel economically viable technique with large-scale production capabilities in modern day micro technologies. The current trends are to extend the potential of the electrodeposition to nano fabrication. We have successfully electrodeposited Cu/Co multilayers, exhibiting appreciably high GMR, on ITO as well as on Cu/Si substrates. Multilayer stacks with films in thickness range 1 – 10 nm were deposited. The Co layers have different mechanisms of growth on these substrates, thus resulting in different microstructure and topography of the electrodeposited films. This leads to different GMR behavior of the multilayers in both these cases. Room temperature GMR values of 15% at low fields are obtained on ITO substrate and higher values are possible on Cu/Si substrate.

Electrical conduction behavior of ultrathin (5–110 nm) SnO2 films reactively sputtered at 150–400 °C substrate temperatures is presented. The surface roughness studies revealed that the films with lower thickness were smoother (≤0.6 nm). Stoichiometry/defect structure of the films obtained from X-ray photoelectron spectroscopy data and electron mobility are found to be dependent on film thickness and substrate temperature. The observed increase in conductivity of semi-metallic films with decrease in film thickness is attributed to changes in defect structure and surface roughness. Highest value of conductivity of about 715 Ω−1 cm−1 is obtained for 5 nm thick films deposited at 300 °C.

The charged state of bismuth atoms in n‐type bismuth‐modified amorphous thin films of Ge20Se80 and As2Se3 has been studied by x‐ray photoelectron spectroscopy. On the basis of the observed chemical shift, it is concluded that the Bi atoms in the modified films are positively charged. The charged Bi atoms perturb the equilibrium between positively and negatively charged defect centers, thereby causing a shift of the Fermi level towards the conduction band. The observed enhanced electrical conductivity and the conductivity conversion from p to n type in the modified films is the result of such a Fermi level shift.

In this work dc-magnetization, electronic structural, and Raman investigations of Ti1−xMnxO2 (x = 0.00, 0.05, 0.10, and 0.15) thin films deposited on fused-quartz substrate by a simple and cost effective spray pyrolysis technique have been reported. X-ray diffraction revealed the formation of pure anatase TiO2 phase devoid of elemental Mn clusters in all the Mn incorporated TiO2 films. It is established by x-ray photoelectron spectroscopic (XPS) measurements that Ti ions substituted by Mn ions in both divalent and trivalent states in the TiO2 matrix. No peak corresponding to Mn+4 could be evidenced by XPS. The Raman study has further established the formation of TiO2 in anatase structure in both pure TiO2 and Mn-doped TiO2 films. The Ti1−xMnxO2 films with x ≥ 0.05 exhibit ferromagnetic ordering at room temperature which arises most likely due to formation of bound magnetic polarons.

We report here the room temperature ferromagnetic ordering in spray-pyrolized polycrystalline thin films of Ti1−xCoxO2 (x = 0, 0.025, 0.05 and 0.10). The saturation magnetic moment in these films with x = 0.05 and 0.10 is estimated to be of 0.28 and 0.38µB/Co, respectively. The ambient air employed in the present case of the spray pyrolysis process resulted in ferromagnetic films possessing very high resistivity values (∼10 7 � cm). This is in contrast to Ti1−xCoxO2 films deposited by vacuum based techniques, which are relatively conducting. While pristine TiO2 film exhibited the anatase phase, the rutile phase of TiO2 also evolved with an increase in Co concentration in these films. X-ray diffractograms could not reveal segregation of Co atoms in the TiO2 matrix; also, no formation of any oxide of cobalt was detected. X-ray photoelectron spectroscopic investigation established the Co cations to be bivalent, and suggests that Co +2 is substituting Ti +4 in the TiO2 matrix. Due to the highly resistive nature of these films, the observed room temperature ferromagnetism could be attributed either to the formation of bound magnetic polarons or to defect mediated ordering.

Magnetic ordering in Co-substituted spray pyrolyzed SnO2 thin films has been investigated by magneto-transport studies of Sn1−xCoxO2−δ and F co-doped films. The free carrier concentration and room temperature ferromagnetism induced in Sn1−xCoxO2−δ thin films with cobalt concentrations up to x = 0.10 are found to be closely related to each other. Both the carrier concentration and the saturation magnetic moment increase monotonically with the concentration of Co, and attain maximum values of 2.2 × 1019 cm−3 and 0.26 μB/Co-ion, respectively, at x = 0.10. The substitution of O2− with F− (nearly 10 atomic percent (a/o)) has resulted in much higher values of both carrier concentration (2.07 × 1020 cm−3) and magnetic moment (0.80 μB/Co-ion). Also, anomalous behavior of the Hall effect has been observed. The carrier mediated interaction is proposed to be the most probable mechanism responsible for ferromagnetism in these films. The temperature dependence of the magnetization of these films predicts a Curie temperature exceeding 573 K. All the films are optically transparent (>75%) in the visible spectral region.

It has been possible to induce room temperature ferromagnetism, exhibiting high transition temperature, in tin oxide thin films by introducing manganese in a SnO2 lattice. The observed temperature dependence of the magnetization predicts a Curie temperature exceeding 550 K. A maximum saturation magnetic moment of 0.18±0.04 μB per Mn ion has been estimated for spray pyrolized Sn1−xMnxO2−δ thin films, with x=0.10. For Mn concentration (x) higher than 0.10, the films show linear behavior. The magnetization-versus-field studies indicate that the origin of ferromagnetism lies neither in ferromagnetic metal clusters nor in the presence of metastable phases. The structure factor calculations reveal that Mn has been incorporated in the SnO2 lattice. Also, the electron transport investigation indicates that there is a change of Mn occupancy from substitutional to interstitial sites of the SnO2 lattice when the Mn concentration exceeds 7.5 at. %. These films do not exhibit anomalous Hall effects at room temperature...

Optical properties of spray pyrolysed Sn1?xCoxO2?? (0?x?0.15) thin films exhibiting room temperature ferromagnetism have been investigated in the energy range 1?6?eV. The onset of optical absorption is blueshifted by as much as 220?meV for a cobalt concentration of 10a/o (x = 0.10). Our detailed analysis indicates that the most probable cause of the blueshift is the Burstein?Moss effect. The optical conductivity calculations reveal that Co does not introduce any mid-gap states. Also the small change in the slope of ?2 versus h? indicates that the O and Sn band edges are affected on Co addition. This band-edge shift also implies the presence of strong Coulomb interaction between Co, Sn and O sites, as a plausible cause of the observed ferromagnetism in these samples. The Burstein?Moss effect seems to be masking the effect of band structure modification introduced by Co addition. The high (~75%) optical transparency of these films in the visible region remains practically unaffected on Co addition.

A maximum room temperature ferromagnetic moment of 0.47μB∕Co ion has been observed in Sn0.9Co0.1O2−δ films grown by spray pyrolysis. The films have high conductivity (∼150Ω−1cm−1) and ∼70% transmittance in the visible region. A systematic variation of saturation magnetization, carrier concentration, electrical conductivity, and optical transmission edge in Sn1−xCoxO2−δ(0.05⩽x⩽0.15) films is correlated with the change in Co concentration, and a carrier mediated Ruderman-Kittel-Kasuya-Yoshida interaction has been proposed as the most probable mechanism for the ferromagnetic ordering. The maximum blueshift in the transmission edge by ∼215meV (at x=0.10) is attributed to the extra carriers generated by Co substitution.

Fluctuation effects and temperature dependance of IV characteristics of c-axis oriented YBCO thin films on STO(100) have been investigated within the context of unbinding of vortex-antivortex pairs in the Kosterlitz-Thouless transition (KT) and Aslamazov-Larkin (AL) model. A critical jump in the nonlinearity parameter, α (V=Iα), is found at the universal value of α = 3. The broadening of the jump in the temperature dependance of α and associated exponential inverse square root temperature dependance of resistivity above Tc indicate quasi bi-dimensional behavior in the YBCO system. The correlation between AL fluctuations and phase fluctuations (KT model) has also been studied.

Thin films of Cu-Co alloy exhibiting excellent metallic luster were galvanostatically electrodeposited directly on Si substrates in a single citrate bath containing sulfates of the metal ions. The direct electrodeposition onto n-Si substrates eliminated a processing step, of depositing a conducting layer, if an insulator were to be used as a substrate. In addition, the use of silicon as a substrate is promising in integrating this inexpensive technique with semiconductor microelectronic device fabrication technology. The as-deposited films exhibited giant magnetoresistance (GMR) of 1% (T = 300 K, H = 10 kOe) and 5% (T = 10 K and H = 50 kOe). The annealed films showed an increase in GMR from I to 2.7%. The X-ray diffraction studies of as-deposited metastable films indicate solid solution like behavior following Vegard's law. However, our magnetic studies evidenced the presence of very fine nanograins of Co in these films. A systematic study of the effect of various processing parameters like deposition current density, bath temperature, and pH on the composition, structure, and microstructure of thin films was carried out to understand the electrodeposition process. Deposition current density and bath temperature have significant control over the composition and microstructure. The pH of the electrolyte seems to affect the topography most. Like physical vapor deposition (PVD), the electrodeposition process yields thin films via a nucleation-controlled growth mechanism. The superiority of the electrodeposition technique over the PVD technique is emphasized.

Physical properties of hydrogenated amorphous silicon (a-Si:H) films prepared ion beam sputtering under varying H 2 :Ar flow ratios and various substrate temperatures are reported. Ellipsometric studies reveal that both the increase in H 2 :Ar flow ratio and decrease in substrate temperature lead to density-deficit films. The films are poorly photoconducting due to the presence of defect centres created possibly by SiH 2 , (SiH) 2 n and SiO species in the midgap.

Electrical, optical, and structural properties of hydrogenated amorphous germanium (a‐Ge:H) films prepared by reactive ion beam sputtering of a high‐purity crystalline germanium target under varying deposition conditions have been studied. A detailed description of the deposition setup, preparation procedures, and techniques of property measurement is given. The dependencies on beam voltage, H2:Ar flow ratio, and substrate temperature of the room‐temperature dark conductivity, optical band gap, hydrogen content, and ellipsometric and IR data are reported and analyzed. The minimum conductivity (10−4 Ω−1 cm−1) a‐Ge:H films have been obtained for H2:Ar flow ratio of 16:1, and beam voltage and substrate temperature of 1000 V and 250 °C, respectively. These films contain a hydrogen concentration of about 11 at. % and show an optical band gap near 1.04 eV. The IR spectra reveal absorption bands corresponding to both monohydride (Ge‐H) and dihydride (GeH2) groups for all the samples deposited. The monohydride ab...

Thin films of hydrogenated amorphous silicon‐germanium (a‐Si1−xGex: H) alloys have been prepared by reactive ion beam sputtering of a composite target of silicon and germanium. The dependence of the deposition rate, conductivity‐temperature variation, optical absorption coefficient, refractive index, imaginary part of the dielectric constant, hydrogen content, and infrared (IR) absorption spectra on germanium content (x) are reported and analyzed. For a typical composition—a‐Si28Ge72:H (x=0.72), the effect of beam voltage, H2:Ar flow ratio, and substrate temperature on the material properties have also been investigated. For the films prepared with increasing x, the expected behavior of a decrease in both hydrogen content and band gap and an increase in the electrical conductivity have been observed. The films prepared at x>0.80 are found to be more homogeneous than the films deposited at 0.0

Hydrpgenated amorphous germanium-carbon (a-Ge1−xCx:H) thin films have been prepared by an Activated Reactive Evaporation (ARE) technique. Germanium was evaporated from a resistively heated tungsten basket through an acetylene plasma. The films thus obtained were characterized for the compositional, structural, electrical and optical properties. The effects of substrate temperature, role of hydrogen and variation of optical energy gap with carbon content were also investigated. Typically, films deposited at 200 °C showed a sharp absorption edge corresponding to an optical gap of about 1.3 eV and thermally activated electrical conduction over a wide range of temperatures.

Etude du comportement d'une cellule solaire a barriere du Schottky formee entre un metal (bismuth) et un chalcogenure semiconducteur amorphe de type n(As 2 Se 3 :Bi). Mesure de la variation thermique de la caracteristique courant d'obscurite-tension, du facteur d'idealite de la diode et de la densite de courant pour une polarisation en sens direct particuliere