Platinum surface additive based nanostructured CuO films for ethanol sensing

In the present work, Platinum (Pt)/Copper (II) oxide (CuO) thin film based ethanol sensors were fabricated by sputtering of Pt in varying concentrations over pre-sputtered nanostructured CuO films. The responses of these sensors as a function of Pt concentrations were studied using operating temperature modulation (200-450 °C) and ethanol concentration modulation (100-2500 ppm). During these modulations, it was found that the sensing response was maximum at operating temperature near 400 °C for all the samples irrespective of the Pt concentration dispersed over them. Moreover, the sensing behavior improves for lower Pt concentration (Pt/CuO-60s) and deteriorates for higher Pt concentration (Pt/CuO-120s). In comparison with bare CuO sample, the sensitivity of Pt/CuO-60s increased up to 22% in the linear range and 33% for maximum ethanol concentration. Hence, the well dispersed optimum Pt additive concentration improves the overall sensing behavior including sensitivity, linear working range and response as well as recovery time.

Sputter Deposited High Capacity Li2-xMnO3-y Films for Thin Film Battery Application

Lithium manganese oxide (Li2-xMnO3-y) thin films have been deposited from activated Li2MnO3 powder by radio frequency magnetron sputtering for the first time in the literature and subjected to electrochemical characterization. Physicochemical characterization by X-ray diffraction has revealed the formation of the thin films with crystallographic phase identical to that of the powder target made of Li2-xMnO3-y. The Li:Mn atomic ratio for the powder and film are calculated by X-ray photoelectron spectroscopy and it is found to be 1.6:1.0. From galvanostatic charge discharge studies, a specific discharge capacity of 139 mu Ah mu m(-1) cm(-2) was obtained when cycled between 2.00 and 3.50 V vs Li/Li+. Additionally the rate capability of the thin film electrodes was studied by subjecting the cells to charge-discharge cycling at different current densities in the range from 10 mu A cm(-2) to 100 mu A cm(-2). (C) 2013 The Electrochemical Society. All rights reserved.

Effect of chemical treatment on surface characteristics of sputter deposited Ti-rich NiTi shape memory alloy thin-films

NiTi thin-films were deposited by DC magnetron sputtering from single alloy target (Ni/Ti: 45/55 aL.%). The rate of deposition and thickness of sputter deposited films were maintained to similar to 35 nm min(-1) and 4 mu m respectively. A set of sputter deposited NiTi films were selected for specific chemical treatment with the solution comprising of de-ionized water, HF and HNO3 respectively. The influence of chemical treatment on surface characteristics of NiTi films before and after chemical treatment was investigated for their structure, micro-structure and composition using different analytical techniques. Prior to chemical treatment, the composition of NiTi films using energy dispersive X-ray dispersive spectroscopy (EDS), were found to be 51.8 atomic percent of Ti and 48.2 atomic percent of Ni. The structure and morphology of these films were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD investigations, demonstrated the presence of dominant Austenite (110) phase along with Martensite phase, for untreated NiTi films whereas some additional diffraction peaks viz. (100), (101), and (200) corresponding to Rutile and Anatase phase of Titanium dioxide (TiO2) along with parent Austenite (110) phase were observed for chemically treated NiTi films. FTIR studies, it can be concluded that chemically treated films have higher tendency to form metal oxide/hydroxide than the untreated NiTi films. XPS investigations, demonstrated the presence of Ni-free surface and formation of a protective metal oxide (TiO2) layer on the surface of the films, in both the cases. The extent of the formation of surface oxide layer onto the surface of NiTi films has enhanced after chemical treatment. (C) 2014 Elsevier B.V. All rights reserved.

Effect of post-deposition annealing on transverse piezoelectric coefficient and vibration sensing performance of ZnO thin films

The present experimental study investigates the influence of post-deposition annealing on the transverse piezoelectric coefficient (d(31)) value of ZnO thin films deposited on a flexible metal alloy substrate, and its relationship with the vibration sensing performance. Highly c-axis oriented and crystalline ZnO thin films were deposited on flexible Phynox alloy substrate via radio frequency (RF) reactive magnetron sputtering. ZnO thin film samples were annealed at different temperatures ranging from 100 degrees C to 500 degrees C, resulting in the temperature of 300 degrees C determined as the optimum annealing temperature. The crystallinity, morphology, microstructure, and rms surface roughness of annealed ZnO thin films were systematically investigated by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and Atomic Force Microscopy (AFM), respectively. The piezoelectric d(31) coefficient value was measured by 4-point bending method. ZnO thin film annealed at 300 degrees C was highly c-axis oriented, crystalline, possesses fine surface morphology with uniformity in the grain size. This film showed higher d(31) coefficient value of 7.2 pm V-1. A suitable in-house designed and developed experimental set-up, for evaluating the vibration sensing performance of annealed ZnO thin films is discussed. As expected the ZnO thin film annealed at 300 degrees C showed relatively better result for vibration sensing studies. It generates comparatively higher peak output voltage of 147 mV, due to improved structural and morphological properties, and higher piezoelectric d(31) coefficient value. (C) 2014 Elsevier B. V. All rights reserved.

Titanium nitride thin film anode: chemical and microstructural evaluation during electrochemical studies

TIN thin films with (200) fibre texture are deposited on Cu substrate at room temperature using reactive magnetron sputtering. They exhibit a discharge capacity of 172 mu Ah cm(-2) mu m(-1) (300 mAh g(-1)) in a non-aqueous electrolyte containing a Li salt. There is a graded decrease in discharge capacity when cycled between 0.01 and 3.0 V. Electron microscopy investigations indicate significant changes in surface morphology of the cycled TiN electrodes in comparison with the as deposited TiN films. From XPS depth profile analysis, it is inferred that Li intercalated TIN films consist of lithium compounds, hydroxyl groups, titanium sub oxides and TiN. Lithium diffusivity and reactivity decrease with increase in depth and the major reaction with lithium takes place at film surface and grain boundaries. (C) 2014 Elsevier Ltd. All rights reserved.

Effect of Substrate Temperature on the Microstructure Variation in Sputter-deposited Hydrogenated Amorphous Silicon Thinfilms

Vacancy, void incorporation and Si-H-x configuration in hydrogenated amorphous silicon (a-Si:H) thin films was studied. Films were grown by Direct Current (DC), pulsed DC and Radio Frequency (RF) magnetron sputtering. Fourier Transform Infrared (FTIR) spectroscopic analysis has been carried out on the films and found that, the a-Si: H films grown by DC magnetron sputtering are of good quality compared to pulsed DC and RF deposited films. The effect of Substrate temperature (T-S) on the total hydrogen concentration (C-H), configuration of hydrogen bonding, density (decided by the vacancy and void incorporation) and the microstructure factor (R*) was studied. T-S is found to be an active parameter in affecting the above said properties of the films. The films contain both vacancies and voids. At low hydrogen dilutions the films are vacancy dominated and at high hydrogen dilutions they are void dominated. It is found that T-S favors monohydride (Si-H) bonding at the cost of dihydride (Si-H-2) bonding. This dividing line is at C-H=14 at.% H for DC sputter deposited films. The microstructure structure factor R* is found to be zero for as deposited DC films at T-S=773K. The threshold C-H for void dominated region is found to be C-H=23 at.% H for RF, C-H=18 at.% H for PDC and C-H similar to 14 at.%H for DC sputter deposited films.

Evaluation. of Transverse Piezoelectric Coefficient of ZnO Thin Films Deposited on Different Flexible Substrates: A Comparative Study on the Vibration Sensing Performance

We report on the systematic comparative study of highly c-axis oriented and crystalline piezoelectric ZnO thin films deposited on four different flexible substrates for vibration sensing application. The flexible substrates employed for present experimental study were namely a metal alloy (Phynox), metal (aluminum), polyimide (Kapton), and polyester (Mylar). ZnO thin films were deposited by an RF reactive magnetron sputtering technique. ZnO thin films of similar thicknesses of 700 +/- 30 nm were deposited on four different flexible substrates to have proper comparative studies. The crystallinity, surface morphology, chemical composition, and roughness of ZnO thin films were evaluated by respective material characterization techniques. The transverse piezoelectric coefficient (d(31)) value for assessing the piezoelectric property of ZnO thin films on different flexible substrates was measured by a four-point bending method. ZnO thin films deposited on Phynox alloy substrate showed relatively better material characterization results and a higher piezoelectric d(31) coefficient value as compared to ZnO films on metal and polymer substrates. In order to experimentally verify the above observations, vibration sensing studies were performed. As expected, the ZnO thin film deposited on Phynox alloy substrate showed better vibration sensing performance. It has generated the highest peak to peak output voltage amplitude of 256 mV as compared to that of aluminum (224 mV), Kapton (144 mV), and Mylar (46 mV). Therefore, metal alloy flexible substrate proves to be a more suitable, advantageous, and versatile choice for integrating ZnO thin films as compared to metal and polymer flexible substrates for vibration sensing applications. The present experimental study is extremely important and helpful for the selection of a suitable flexible substrate for various applications in the field of sensor and actuator technology.

Pulsed rf magnetron sputtered alumina thin films

Alumina thin films were deposited on titanium (Ti) and fused quartz by both direct and reactive pulsed rf magnetron sputtering techniques. X-ray diffraction, field emission scanning electron microscopy, energy dispersive X-ray spectroscopy and atomic force microscopy were utilized to study the phases and surface morphology of the films. The as-deposited alumina thin films were amorphous. However, after annealing at 500 degrees C in vacuum, the crystalline peaks corresponding to the Theta (0), Delta (8) and Chi ()) alumina phases were obtained. The optical transmittance and reflectance as well as IR emittanc,e data were also evaluated for the thin films. The transmittance, e.g., (similar to 90%) of the bare quartz substrate was not changed even when the alumina thin films were deposited for an hour. However, further increase in deposition time (e.g., 7 h) of the alumina thin films showed only a marginal decrease (e.g., similar to 5%) in average transmittance of the bare quartz substrate. The direct and indirect optical band gaps and extinction coefficient of the alumina films were estimated from the transmittance spectra. The IR emittance of the Ti substrate (e.g., similar to 16%) was almost constant after depositing alumina thin films for an hour. Further increase in deposition time showed only a marginal increase (e.g., similar to 9%) in IR emittance value. Therefore, it is proposed that the alumina films developed in the present work can act as a protective cover for the Ti substrate while retaining the thermo-optical properties of the same. The nanohardness and Young's modulus of the alumina thin films were evaluated by the novel nanoindentation technique. The nanohardness was measured as similar to 6 GPa. Further, Young's modulus was evaluated as similar to 116 GPa. The magnitudes of the nanomechanical properties of the thin films were a little smaller than those reported in the literature. This was linked to the lack of crystalline phases in the as-deposited alumina thin films. (C) 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

Effect of Post-Deposition Annealing on the Al2O3/Si(100) Interface Properties

In the present investigation, Al2O3 thin films were deposited onto Si < 100 > substrates by DC reactive magnetron sputtering. The films were annealed in vacuum for one hour at 623, 823 and 1023 K. The composition of the films was quantitatively estimated using X-ray photoelectron spectroscopy (XPS) and the O/Al ratio was found be in the range 1.19 to 1.43. Grazing incidence X-ray diffraction (GIXRD) results revealed that the annealed films are amorphous in nature. Cross sectional transmission electron microscopy (X-TEM) analysis was carried out to study the microstructure and nature of the Al2O3-Si interface as a function of post-deposition annealing. TEM results revealed the presence of nanocrystalline gamma-Al2O3 in the annealed films and an amorphous interface layer was observed at the Al2O3 Si interface. The thickness of the amorphous interface layer was determined from the TEM analysis and the results are discussed.

Effect of post-deposition annealing on composition and electrical properties of dc reactive magnetron sputtered Al2O3 thin films

We have investigated the effect of post- deposition annealing on the composition and electrical properties of alumina (Al2O3) thin films. Al2O3 were deposited on n-type Si < 100 >. substrates by dc reactive magnetron sputtering. The films were subjected to post- deposition annealing at 623, 823 and 1023 K in vacuum. X-ray photoelectron spectroscopy results revealed that the composition improved with post- deposition annealing, and the film annealed at 1023 K became stoichiometric with an O/Al atomic ratio of 1.49. Al/Al2O3/Si metal-oxide-semiconductor (MOS) structures were then fabricated, and a correlation between the dielectric constant epsilon(r) and interface charge density Q(i) with annealing conditions were studied. The dielectric constant of the Al2O3 thin films increased to 9.8 with post- deposition annealing matching the bulk value, whereas the oxide charge density decreased to 3.11 x 10(11) cm(-2.) Studies on current-voltage IV characteristics indicated ohmic and Schottky type of conduction at lower electric fields (<0.16 MV cm(-1)) and space charge limited conduction at higher electric fields.

Influence of sputter power on structural and electrical properties of TiO2 films for Al/TiO2/Si gate capacitors

Titanium dioxide (TiO2) thin films were deposited onto p-Si substrates held at room temperature by reactive Direct Current (DC) magnetron sputtering at various sputter powers in the range 80-200W. The as-deposited TiO2 films were annealed at a temperature of 1023K. The post-annealed films were characterized for crystallographic structure, chemical binding configuration, surface morphology and optical absorption. The electrical and dielectric properties of Al/TiO2/p-Si structure were determined from the capacitance-voltage and current-voltage characteristics. X-ray diffraction studies confirmed that the as-deposited films were amorphous in nature. After post-annealing at 1023K, the films formed at lower powers exhibited anatase phase, where as those deposited at sputter powers >160W showed the mixed anatase and rutile phases of TiO2. The surface morphology of the films varied significantly with the increase of sputter power. The electrical and dielectric properties on the air-annealed Al/TiO2/p-Si structures were studied. The effect of sputter power on the electrical and dielectric characteristics of the structure of Al/TiO2/p-Si (metal-insulator-semiconductor) was systematically investigated. Copyright (c) 2014 John Wiley & Sons, Ltd.

Fabrication and characterization of gold coated hollow silicon microneedle array for drug delivery

In this paper, we present the fabrication and characterization of Ti and Au coated hollow silicon microneedles for transdermal drug delivery applications. The hollow silicon microneedles are fabricated using isotropic etching followed by anisotropic etching to obtain a tapered tip. Silicon microneedle of 300 mu m in height, with 130 mu m outer diameter and 110 mu m inner diameter at the tip followed by 80 mu m inner diameter and 160 mu m outer diameter at the base have been fabricated. In order to improve the biocompatibility of microneedles, the fabricated microneedles were coated with Ti (500 nm) by sputtering technique followed by gold coating using electroplating. A breaking force of 225 N was obtained for the fabricated microneedles, which is 10 times higher than the skin resistive force. Hence, fabricated microneedles can easily be inserted inside the skin without breakage. The fluid flow through the microneedles was studied for different inlet pressures. A minimum inlet pressure of 0.66 kPa was required to achieve a flow rate of 50 mu l in 2 s with de-ionized water as a fluid medium. (C) 2014 Elsevier B.V. All rights reserved.

CuIn1-xAlxSe2 Solar Cells Fabricated on the Flexible Substrates by CoSputtering and Modified Selenization

CuIn1-xAlxSe2 (CIAS) thin films were grown on the flexible stainless steel substrates, by de co-sputtering from the elemental cathodes. CuInAl alloyed precursor films were selenized both by noble gas assisted Se vapor transport and vacuum evaporation of Se. X-ray diffraction, scanning electron microscopy and UV-visible absorption spectroscopy were used to characterize the selenized films The composition (x=Al/Al+In) with 0 <= x <= 0.65 was varied by substituting Al with indium in CuInSe2. Lattice parameters, average crystallite sizes and compact density of the films compared to CuInSe2, decreased and (112) peak shifted to higher Bragg's angle, with Al incorporation. Cells were fabricated with the device structure SS/Mo/CIAS/CdS/iZno-AZO/Al. Best cell showed the efficiency of 6.8%, with x=0.13, Eg=1.17 eV, fill factor 45.04, short circuit current density J 30 mA/cm(2).

Room temperature ferromagnetic and ferroelectric properties of Bi1-xCaxMnO3 thin films

Bi1-xCaxMnO3 (BCMO) thin films with x = 0, 0.1, 0.2, 0.3 and 0.4 are successfully deposited on the n-type Si (100) substrate at two different temperatures of 400 degrees C and 800 degrees C using RF magnetron sputtering. The stoichiometry of the films and oxidation state of the elements have been described by X-ray photoelectron spectroscopy analysis. Dielectric measurement depicts the insulating property of BCMO films. Magnetic and ferroelectric studies confirm the significant enhancement in spin orientation as well as electric polarization at room temperature due to incorporation of Ca2+ ions into BiMnO3 films. The BCMO (x = 0.2) film grown at 400 degrees C shows better magnetization (M-sat) and polarization (P-s) with the measured values of 869 emu / cc and 6.6 mu(C)/cm(2) respectively than the values of the other prepared films. Thus the realization of room temperature ferromagnetic and ferroelectric ordering in Ca2+ ions substituted BMO films makes potentially interesting for spintronic device applications. (C) 2014 Author(s).

An insight to the low temperature conduction mechanism of c-axis grown Al-doped ZnO, a widely used transparent conducting oxide

Al-doped ZnO thin films were synthesized from oxygen reactive co-sputtering of Al and Zn targets. Explicit doping of Al in the highly c-axis oriented crystalline films of ZnO was manifested in terms of structural optical and electrical properties. Electrical conduction with different extent of Al doping into the crystal lattice of ZnO (AZnO) were characterized by frequency dependent (40 Hz-50 MHz) resistance. From the frequency dependent resistance, the ac conduction of them, and correlations of localized charge particles in the crystalline films were studied. The dc conduction at the low frequency region was found to increase from 8.623 mu A to 1.14 mA for the samples AZnO1 (1 wt% Al) and AZnO2 (2 wt% Al), respectively. For the sample AZnO10 (10 wt% Al) low frequency dc conduction was not found due to the electrode polarization effect. The measure of the correlation length by inverse of threshold frequency (omega(0)) showed that on application of a dc electric field such length decreases and the decrease in correlation parameter(s) indicates that the correlation between potentials wells of charge particles decreases for the unidirectional nature of dc bias. The comparison between the correlation length and the extent of correlation in the doped ZnO could not be made due to the observation of several threshold frequencies at the extent of higher doping. Such threshold frequencies were explained by the population possibility of correlated charge carriers that responded at different frequencies. For AZnO2 (2% Al), the temperature dependent (from 4.5 to 288 K) resistance study showed that the variable range hopping mechanism was the most dominating conduction mechanism at higher temperature whereas at low temperature region it was influenced by the small polaronic hopping conduction mechanism. There was no significant influence found in these mechanisms on applications of 1, 2 and 3 V as biases.