Effect Of Post-deposition Heat Treatment Research Articles

High Efficiency Sputtered CdS/CdTe Cells without CdCl2 Activation

ABSTRACTPolycrystalline thin-film CdS/CdTe PV cells nearly always require “activation” with vapors containing chlorine and oxygen near 400 oC in order to realize the highest cell performance, even when growth occurs near 600 oC. In this study we have used film growth near 270 oC by magnetron sputtering in an oxygen-free ambient and have studied the effects of post-deposition heat treatments for 20 minutes at 400, 425 and 450 oC without CdCl2 in a dry air ambient. The heat treatments enhanced grain growth and produced re-crystallization of the CdTe film at all three temperatures, but 450 oC was required to reach the best electrical performance. Grain size increased from a couple of hundred nanometers to more than a micron as the preferred (111) growth orientation decreased. Efficiencies up to 11.6% were achieved with no CdCl2 compared to ~13% with activation at 387 oC in the presence of CdCl2 vapors. X-ray diffraction and quantum efficiency measurements show interdiffusion of CdS and CdTe at 450 oC comparable with a standard CdCl2 treatment at 387 oC. The results are discussed in terms of CdSTe alloy gradients and minority-carrier diffusion lengths.

Effect of heat treatment on mechanical dissipation in Ta2O5 coatings

Thermal noise arising from mechanical dissipation in dielectric reflective coatings is expected to critically limit the sensitivity of precision measurement systems such as high-resolution optical spectroscopy, optical frequency standards and future generations of interferometric gravitational wave detectors. We present measurements of the effect of post-deposition heat treatment on the temperature dependence of the mechanical dissipation in ion-beam sputtered tantalum pentoxide between 11 K and 300 K. We find that the temperature dependence of the dissipation is strongly dependent on the temperature at which the heat treatment was carried out, and we have identified three dissipation peaks occurring at different heat treatment temperatures. At temperatures below 200 K, the magnitude of the loss was found to increase with higher heat treatment temperatures, indicating that heat treatment is a significant factor in determining the level of coating thermal noise.

Effect of Postdeposition Heat Treatment on the Crystallinity, Size, and Photocatalytic Activity of TiO2 Nanoparticles Produced via Chemical Vapour Deposition

Titanium dioxide (TiO2) nanoparticles were produced using chemical vapour deposition (CVD) at different deposition temperatures (300–700°C). All the samples were heat treated at their respective deposition temperatures and at a fixed temperature of 400°C. A scanning electron microscope (SEM), a transmission electron microscope (TEM), and X‐ray diffraction (XRD) were used to characterize the nanoparticles in terms of size and crystallinity. The photocatalytic activity was investigated via degradation of methylene blue under UV light. The effects of post deposition heat treatment are discussed in terms of crystallinity, nanoparticle size as well as photocatalytic activity. Crystallinity was found to have a much larger impact on photocatalytic activity compared to nanoparticle size. Samples having a higher degree of crystallinity were more photocatalytically active despite being relatively larger in size. Surprisingly, the photocatalytic activity of the samples reduced when heat treated at temperatures lower than the deposition temperature despite showing an improvement in crystallinity.

Effect of post-deposition heat treatment on the sliding wear resistance of a nickel-based coating deposited using high velocity oxy-fuel

In the present research, a nickel base coating was deposited on an AISI 1020 substrate using a high-velocity oxy-fuel technique. The coating was subsequently heat treated (HT) by means of an oxyacetylene flame. For the conditions evaluated in the present study, it was found that the HT coating has 1.15 times better wear resistance for the lower level of applied load and lower sliding speed (SS), and nearly 50 times better resistance for the highest level of the applied load and highest SS when compared with the non-HT coatings. These results have been attributed to a better distribution of the hardening phases, better cohesion between particles and an increase in hardness, as a consequence of the post-deposition heat treatment process. A severe wear regime was found for all the samples, since the wear rates presented values which were higher than 1 × 10− 5 mm3/m. The presence of the adhesion, oxidization, three-body abrasion, and cyclical deterioration phenomena, all competing with each other, was noted. For the HT coatings, the wear mechanism was mainly due to the adhesion and oxidisation phenomena, while for the steel counterpart mechanisms such as oxidization, grooving and three-body abrasion were observed.

Effect of heat treatment on ITO film properties and ITO/p-Si interface

The effect of post-deposition heat treatment on ITO/p-Si heterostructures grown at room temperature by dc magnetron sputtering has been studied. Structural, electrical and optical properties of the films as well as the electronic properties of the ITO/Si interface are investigated for annealing in the temperature range 100–400 °C in air. X-ray analysis indicates that the as-deposited films are predominantly amorphous with poor optical transmittance and electrical conductivity. The electronic quality of the ITO/Si interface for the as-deposited film, characterized by current–voltage ( I– V) and capacitance–voltage ( C– V), is also found to be poor. Annealing at 100–300 °C results in improvement of structural, electronic and optical properties of the ITO films. For instance, the resistivity of the ITO films is found to decrease to a value of 2.5 × 10 −4 Ω cm after heat treatment at 300 °C. This correlates with improvement of the electronic quality of the ITO/Si interface. Heat treatments at 400 °C, however, result in degradation of the interface and the electrical properties of the films.

Effect of post-deposition heat treatment on mechanical properties of thermally sprayed hydroxyapatite coating

This paper mainly deals with the inner microstructure and mechanical performance of plasma sprayed hydroxyapatite (HA) coatings before and after heat treatment. The electron probe microanlyser shows that some regions with different contrasts exist in the as-sprayed coatings. Under the back scattering electron (BSE) model, the origin particles of HA are well melted, and there are the more inhomogeneites in the as-sprayed coatings. Heat treatment can eliminate the regions with different contrasts and improve the crystallinity of the coatings. Some coatings were immersed into 50 mL deionised water under constant 37°C condition for 20 days. After the immersion in the deionised water, new layers with dot like precipitates formed on the surface of the as-sprayed coatings and the inhomogeneities were eliminated. For as-sprayed coatings, the amount of precipitates on the surface of low crystalline coatings is larger than that of high crystalline coatings. For post-heat treated coatings, there are no other phases but β-Ca2P2O7 precipitates along the cracks paths. The shear strength of as-sprayed coatings of low crystallinity is higher than that of high crystalline coatings. In this paper, post-heat treatment can improve the shear strength of coarse coatings but decrease that of fine coatings.

Effects of post-deposition heat treatment and hydrogenation on electrical conductivity of nanodiamond films

Effects of post-deposition hydrogenation on electrical conductivity of intrinsic and nitrogen doped nanodiamonds have been characterized. Nanodiamond films were deposited by means of microwave plasma assisted chemical vapor deposition in gas mixtures of methane and argon with little or without hydrogen additives. For nitrogen doped nanodiamonds, nitrogen gas of varied flow rates was added to the gas mixture of methane and argon as a dopant. Electrical conductivity of as-grown nanodiamond films was measured by either (i) directly measuring the conductivity of a metal/nanodiamond/metal sandwich test structure or (ii) applying an electrical current through two terminals of a van der Pauw test structure while measuring the voltage across the other two terminals on corners of a nanodiamond film that was deposited on an electrically insulating surface of a substrate. The same measurement was repeated after subjecting the nanodiamond to a heat treatment and later repeated again after exposing the nanodiamond to hydrogen plasma. Effects of the heat treatment and the plasma hydrogenation on electrical conductivity of nanodiamond are reported and discussed.

Effects of Postdeposition in situ Heat Treatment on the Properties of Low Dielectric Constant Plasma Polymer Films Deposited Using Decahydronaphthalene and Tetraethyl Orthosilicate as the Precursors

We investigated effects of postdeposition heat treatment (HT) on the properties of plasma polymer films deposited by plasma-enhanced chemical vapor deposition using a mixture of decahydronaphthalene and tetraethyl orthosilicate as the precursors, which were referred to as plasma-polymerized decahydronaphthalene:tetraethyl orthosilicate (PPDHN:TEOS) films. HTs at 350, 450, and 500 °C decreased the relative dielectric constant k of the PPDHN:TEOS films from 3.16, the k value of the as-deposited film, to 2.82, 2.72, and 3.02, respectively. The change of k value as a function of HT temperature was correlated with the change of Fourier transform infrared absorption peaks of O–H, C = O, and Si-related groups. As the HT temperature increased, the thermal stability of the PPDHN:TEOS film increased. PPDHN:TEOS films, as-deposited or heat treated, showed leakage current density in the order of 10−7 A/cm2 at 1 MV/cm.

CRYSTALLIZATION AND OPTOELECTRONIC PROPERTIES OF INDIUM-ZINC-OXIDE THIN FILMS ANNEALED IN ARGON AND VACUUM

Multi-component oxides based on the In 2 O 3 – ZnO system has recently gained much attention as an alternative transparent conducting oxide. In 2 O 3 and ZnO react to form several homologous compounds of the form Zn k In 2 O k+3, some of which possess excellent electrical and optical properties. Although the appearance of an amorphous-like phase has been reported at intermediate Zn/(In + Zn) ratios, little work has been done on the effect of post-deposition heat treatment on such IZO films. In this work, representative samples of IZO deposited in different ambience and conditions by radio-frequency magnetron sputtering exhibiting an amorphous diffraction pattern were annealed in an argon atmosphere of 1.6 × 102 mbar and vacuum of 10-6 mbar at 500°C for 1 hour. XRD and SEM studies of the annealed films showed a marked difference in both the diffraction pattern and surface morphology after annealing. A variety of morphology, including dendrite-like patterns radiating outward was observed. The electrical and optical properties of the IZO films after annealing were also studied. Results show that while crystallinity of the films was improved after annealing, the electrical conductivity was reduced by several orders of magnitude. Annealing also seems to induce the crystallization of multiple phases in IZO films.

Hydroxyapatite-coated Ti–6Al–4V: Part 2: the effects of post-deposition heat treatment at low temperatures

The present investigation explores the effects of a 90-h post-deposition annealing treatment at 400°C in air on the crystallographic and chemical properties of a plasma-sprayed hydroxyapatite (HA) coating, the thickness and composition of the interfacial oxide layer, and the fatigue behaviour of the underlying Ti–6Al–4V substrate. X-ray diffraction analysis revealed that significant recovery of the crystalline HA structure occurred as a result of the treatment, however, as compared with results obtained through treatment at higher temperatures, recovery obtained through use of the present treatment was incomplete. X-ray photoelectron spectroscopy analysis showed no changes in the constituents of the oxide layer, with the oxide species TiO 2, Al 2O 3, V 2O 5, V 2O 3, and VO 2 present on both the as-sprayed and the heat-treated substrates. A change in film thickness was observed, however, as evidenced by a change in colour from opaque bronze to dark purple. The fatigue resistance of the substrate was found to be significantly reduced by the heat treatment, with the lives of heat-treated coupons with coatings of all thicknesses closely resembling those of as-sprayed coupons with thick HA coatings and uncoated stress-relieved coupons presented in Part 1 of this study. Stress relief was identified as the most likely cause of these reductions.

Surface Evolution of NiTi and NiTiHf Thin Films

AbstractThe microstructure evolution of Ti-rich NiTi thin films and (TiHf)-rich NiTiHf thin films containing 9at% Hf was investigated. These films were deposited from single NiTi and NiTiHf targets using a DC magnetron sputtering system. Free-standing films were obtained by using single crystal silicon substrates. The thickness of these films was controlled between 10-12 μm. In this investigation, the effects of deposition temperature on the surface and cross-sectional microstructures of these films were studied. Substrate temperature during deposition was varied between 300°C to 700°C at 100°C intervals. The influence of post deposition heat treatment (HT) temperature on the microstructure of these films was also studied. The post deposition HT temperature was varied between 300°C and 800°C at 100°C intervals. Both surface and cross- sectional microstructures were examined using a scanning electron microscope (SEM). The crystallinity and the phases present were determined using x-ray diffractometry. All the as- deposited films were found to be crystalline, even when the substrate temperature was as low as 300°C. Results from the microstructure analysis show that all the films have a relatively fine grain size ranging from 0.2 μm to 2.5 μm, and the grain size increases with increasing substrate deposition temperature. The effect of post deposition HT on grain size was found to be minimal.

Chemical composition, microstructure and magnetic characteristics of yttrium iron garnet (YIG, Ce:YIG) thin films grown by rf magnetron sputter techniques

YIG thin films were grown by rf magnetron sputter techniques. We investigated the effect of post-deposition heat-treatment as well as various deposition parameters such as substrate materials, substrate temperature, sputter power, and sputter gas types on the crystallinity, chemical composition, microstructure and magnetic characteristics of the films. Post-deposition heat-treatment over 750/spl deg/C was applied to crystallize as-prepared amorphous films, and a strong tendency of particular crystallographic planes lying parallel to substrate surface was observed for the heat-treated film on GGG substrate. The chemical composition of the film exhibited a wide range of chemical stoichiometry depending on the oxygen fraction of the sputter gas, and in particular the compositions of the YIG and Ce:YIG films deposited in sputter gas with an oxygen fraction of 20% were Y/sub 2.88/Fe/sub 3.84/O/sub 12/ and Ce/sub 0.24/Y/sub 1.10/Fe/sub 3.50/O/sub 12/, respectively. With raising the temperature of post-deposition heat-treatment from 900/spl deg/C to 1100/spl deg/C, the surface roughness of the film on GGG substrate increased, but coercive force as well as ferromagnetic resonance line width decreased.

The influence of annealing processes on the structural, compositional and electro-optical properties of CuIn0.75Ga0.25Se2 thin films

Crystalline defects, such as the density of voids, grain boundaries and dislocations, in Cu(In,Ga) Se2 absorber layers depend on the fabrication conditions and determine to a large extent the efficiency of photovoltaic devices. The material properties, however, can be improved significantly by using post-deposition processes. In this paper, the effects of post-deposition heat treatments on properties of CuIn0.75Ga0.25Se2 (CIGS) thin films are investigated. Selected flash evaporated samples were subsequently processed under several sets of conditions, including vacuum, selenium, inert (argon) and forming gas (a 9:1 mixture of N2:H2) ambients, at different temperature and times. Structural, compositional and electro-optical properties of both as-deposited and annealed films were studied using a variety of analytical techniques. X-ray diffraction (XRD) and scanning electron microscopy (SEM) studies of the films showed a columnar grain structure with strong preferred orientation, which after heat treatments relaxed to give a chalcopyrite structure. Raman analysis showed that the annealing process reduced the full-wave half-maximum (FWHM) value from 20 to 10 cm−1 indicating a change in both film composition and microstructure. In addition, X-ray fluorescence (XRF) and Rutherford backscattering spectroscopy (RBS) revealed that the composition was approaching that of the polycrystalline starting material. Both n- and p-type conductivities were observed with resistivity values in the range 10−1 to 106 Ω cm. Annealing in selenium atmosphere altered the n-type conductivity to p-type. To confirm improvements in optical properties of annealed films, photoacoustic spectroscopy (PAS) was employed.

Post-deposition treatment effects on hydroxyapatite vacuum plasma spray coatings

The purpose of this work is to evaluate the effects of post-deposition heat treatments on high and low crystallinity hydroxyapatite coatings on Ti6Al4V alloy. HA layers were produced by the vacuum plasma spray (VPS) technique, and the desired degrees of crystallinity were obtained by changing the deposition parameters. An analysis of the mechanical properties of the coatings and their adhesion to the substrate has been done by shear strength test. X-ray diffraction analysis was used to detect the structure and the chemical components in which HA dissociates during the deposition process and heat treatments. The data obtained indicates that heat treatments can increase the crystallinity of HA, but they also introduce a mechanical degradation of the coatings. After heat treatments, it was also observed that a large amount of tetracalcium phosphate was formed.

Effects of post-deposition heat treatments on ZnO/CdS/CuInSe2 thin film solar cells studied by photoluminescence measurements

Abstract The effects of post-deposition heat treatments on MOCVD-ZnO/Dip CdS/Selenized CuInSe 2 (CIS) thin film solar cells were investigated by photoluminescence (PL) measurements. PL measurements indicate the interactions between extrinsic oxygen and a native In Cu antisite defect for the PL peak at about 1340 nm and the presence of a native O Se defect as a donor site probably in the grain boundary for the broad PL peak centered at around 1420 nm. Applying the post-deposition annealing of 150°C for 30 min. in air after CdS deposition, 10.3% efficiency was achieved with the CIS thin film absorber selenized in vacuum with elementary Se vapor.

Effect of annealing on electrical and optical properties of RF magnetron sputtered indium tin oxide films

Indium tin oxide (ITO, 90wt%In 2O 3-10wt%SnO 2) films of ~ 1 μm thick have been deposited on glass substrates by radio-frequency (RF) magnetron sputtering. The effect of post-deposition heat treatment on the electrical and optical properties of ITO films are investigated. Annealing of ITO-coated substrates at a temperature of 350–550°C for 2 h in air causes the ITO layers to crystallize and grains to grow. Tin atoms are activated after annealing and behave as effective donors. The electrical resistivity of ITO film decreases by more than two orders of the magnitude after annealing. The infrared reflectance increases as the annealing temperature is raised. An infrared reflectance of ~ 60% (at 5 μm) is obtained for the 550°C-annealed sample. Several material parameters, such as the effective band gap and the refractive index, have been derived and discussed.

Pressure transducer with Au-Ni thin-film strain gauges

The behavior of a pressure transducer with Au-Ni (89:11) film as strain gauges has been studied. The effects of postdeposition heat treatment on the resistance of the thin-film strain gauges and hence the output performance of the pressure transducer are discussed. The effect of a repeated number of pressure cycles carried out over a period of eight months has also been reported. The maximum nonlinearity and the hysteresis is improved from 0.92% FSO to 0.06% FSO after 1000 pressure cycles. The output behavior of the pressure transducer with temperature has also been studied. >

Effect of post-deposition heat-treatment on physical properties of tin oxide thin films prepared by an electron-beam evaporation technique

As-deposited thin films of SnO 2 with substrate temperatures of 50, 200 and 350°C revealed that the films required an additional step of annealing to change the SnO 2 phase to SnO 2 with acceptable optical and electrical properties. Films deposited at 350°C and annealed at 650°C for 2h met the desired requirements

Grain boundary scattering in aluminium-doped ZnO films

Electrical conductivity and Hall mobility of ZnO:Al films were measured in the temperature range 170–350 K. The effects of post-deposition heat treatment in vacuum and hydrogen atmosphere on the above properties were studied to derive meaningful information on the scattering mechanisms in these films. Grain boundary scattering was found to be the predominant mode of scattering at lower temperatures whereas the contribution from ionized impurities together with phonon scattering become significant at higher temperatures. The density Q t of trap states and its position was determined.

Performance study of a pressure transducer with meandering-path thin film strain gauges

The performance of a pressure transducer with meandering-path thin film strain gauges has been studied. Details of the procedure followed to prepare the thin film strain gauge system on the pressure transducer diaphragm are given. The effect of post-deposition heat treatment on the resistance of the sensing films of the strain gauges and the insulating base layers are discussed. The output of the pressure transducer was studied with various input pressures and excitation voltages. It was found that up to a maximum of 10 V bridge excitation the output was stable and repetitive. The maximum non-linearity and hysteresis observed are ±0.15%, ±0.16% and ±0.14% FSO (full-scale output) for 5, 7.5 and 10 V excitation respectively. Information on the output behaviour of the pressure transducer with temperature is also included.