Effect of annealing on the electrodeposited Cu2O films for photoelectrochemical hydrogen generation

Cu₂O films were electrodeposited on stainless steel substrates followed by Ar annealing for photoelectrochemical hydrogen generation. Plating variables including time and pH for the plating bath were explored to obtain desirable film qualities. X-ray diffraction (XRD) patterns indicated that the as-deposited Cu₂O films exhibited preferred orientations in (200) and (111) planes from the plating bath of pH 9 and pH 11, respectively. Images from scanning electron microscope (SEM) revealed pyramid-like grains in 1 µm size for the Cu₂O films from pH 9 plating bath and large plate-like grains in 3-8 µm size from pH 11 plating bath. Identical results from SEM and XRD were obtained from the Cu₂O films at longer plating time. After annealing at 350 °C for 30 and 60 min, the Cu₂O phase was nicely maintained but SEM images demonstrated coarser grains. Photoelectrochemical activity for H₂ generation was obtained on the Cu₂O films before and after annealing by recording relevant photoelectrochemical currents at − 0.3 V in 0.5 M aqueous Na₂SO₄ solution. For the Cu₂O films from both baths, substantial increments in photoelectrochemical current were observed for the annealed samples as opposed to as-deposited ones. The largest photoelectrochemical current was obtained at 0.143 mA/cm² from the Cu₂O film of pH 9 plating bath with 60 min annealing, which exhibited a 560% increase over the as-deposited sample. We attributed the enhanced photoelectrochemical current to the improved crystallinity and reduced defects for the annealed Cu₂O films.     

Growth kinetics of electroless NixCo1 − x deposition

Various electroless Ni-Co-P films were deposited on silicon substrates in electroless baths using sodium hypophosphite as reducing agent and nickel and cobalt sulfates as ion source at pH value of 9 and temperature from 55 to 85 °C. The effect of the atomic ratio of Co to Ni + Co in baths on the growth behavior of the electroless Ni-Co-P films was studied. The various electroless Ni-Co-P films were characterized by scanning electron microscopy for the morphology, transmission electron microscopy for the microstructure and thickness, and energy dispersion spectroscopy for the composition. The results showed that the growth rate of the electroless Ni-Co-P films is generally increased with increase of the bath temperature and is decreased with atomic ratio of Co to Ni + Co in baths. The reduction of the Co²⁺ ion is easier than the Ni²⁺ ion in various baths, except for the bath with 0.9 atomic ratio of Co to Co + Ni.     

Structures and magnetic properties of electroless Ni multilayers on Fe/Si substrate

Nanosized single and multiple layers of electroless Ni films were deposited on Fe film. The multilayer films consisting of a Fe/(Ni1 Ni2)n structure, where Ni1 and Ni2 denote various electroless Ni films deposited in plating baths with different pH values, and n denotes layer numbers and equals to 2, 4, 8, and 16, were formed by alternately changing the pH value of plating baths under controlled deposition time during the deposition process. The ensuing results showed that the boundaries between films are almost even. The deposition of various electroless Ni films on Fe film can increase the coercivity and squareness ratio of Fe film.     

Alteration of internal stresses in SiO2/Cu/TiN thin films by X-ray and synchrotron radiation due to heat treatment

A break of wiring by stress-migration becomes a problem with an integrated circuit such as LSI. The present study investigates residual stress in SiO₂/Cu/TiN film deposited on glass substrates. A TiN layer, as an undercoat, was first deposited on the substrate by arc ion plating and then Cu and SiO₂ layers were deposited by plasma coating. The crystal structure and the residual stress in the deposited multi-layer film were investigated using in-lab. X-ray equipment and a synchrotron radiation device that emits ultra-high-intensity X-rays. It was found that the SiO₂ film was amorphous and both the Cu and TiN films had a strong {1 1 1} orientation. The Cu and TiN layers in the multi thick (Cu and TiN:1.0 μm)-layer film and multi thin (0.1 μm)-layer film exhibited tensile residual stresses. Both tensile residual stresses in the multi thin-layer film are larger than the multi thick-layer film. After annealing at 400 °C, these tensile residual stresses in both the films increased with increasing the annealing temperature. Surface swelling formations, such as bubbles were observed in the multi thick-layer film. However, in the case of the multi thin-layer films, there was no change in the surface morphology following heat-treatment.     

Effect of heating on the residual stresses in TiN films investigated using synchrotron radiation

The structure and residual stresses of TiN films deposited by arc ion plating (AIP) on a steel substrate were investigated using a synchrotron radiation system that emits ultra-intense X-rays. In a previous study, the crystal structures of TiN films deposited by AIP were found to be strongly influenced by the bias voltage. When high bias voltages were used, TiN films that were approximately 200 nm thickness had a preferred orientation of {110}, whereas TiN films that were approximately 600 nm thickness has a multilayer film orientation of {111}/{110}. In this present study, the two-tilt method was used to evaluate the residual stresses in TiN films by measuring lattice strains in two directions determined by the crystal orientation. Residual stresses in 600-nm-thick as-deposited TiN films were found to be −10.0 GPa and −8.0 GPa for {111}- and {110}-textured layers, respectively, while they were −8.0 GPa for {110}-textured layers in 200-nm-thick as-deposited TiN films. Residual stresses of both films relaxed to thermal stress levels upon annealing.     

TiN/TiC multilayer films deposited by pulse biased arc ion plating

TiN/TiC multilayer films were deposited on high-speed-steel (HSS) substrates using pulse biased arc ion plating. For comparison, TiN and TiC films were also deposited. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and Auger electron spectroscopy (AES) were applied to investigate the modulation period thickness, microstructure and content depth distribution of the films, respectively. And microhardness and film/substrate adhesion were also analyzed using knoop tester and scratching method. The results showed that the multilayer films with different modulation period of 40-240 nm exhibit a modulation structure and the interface width is about 20∼30 nm. Microhardness of the multilayer films were not obviously improved compared to that of TiN and TiC film, and the reason was analyzed. In comparison to TiN film, film/substrate adhesion values of the multilayer films were deteriorated with the increasing of modulation period due to the brittle characteristics of TiC film.     

Comparison of the optical and structural properties of nickel oxide-based thin films obtained by chemical bath and sputtering

Nickel oxide thin films were prepared using chemical bath deposition and reactive magnetron dc-sputtering. Through the chemical route, Ni(OH)₂ films were deposited with a nano-porous structure providing large specific surface area. Subsequent annealing at 300 °C transformed the films into NiO. These films showed high absorption in the visible range and low crystallinity due to Ni vacancies. Annealing at higher temperatures removes Ni vacancies improving transmittance and crystallinity. Sputtered films were obtained in Ar + O₂ and Ar + H₂ + O₂ atmospheres at different flux ratios. During deposition in the former atmosphere, substrate temperature was 300 °C producing dense polycrystalline films with excellent optical properties. In the hydrogen containing atmosphere, the substrate was at room temperature and polycrystalline films with a dark-yellowish color and expanded lattice were obtained.     

Electrodeposition of CuInSe2 absorber layers from pH buffered and non-buffered sulfate-based solutions

CuInSe₂ (CIS) thin films were deposited on Mo/glass substrates by one-step electrodeposition from aqueous baths containing CuSO₄, In₂(SO₄)₃ and SeO₂ with Li₂SO₄ electrolyte. The quality of the electrodeposited films depended on the presence of pH buffer in the bath. CIS films deposited from non-pH buffered baths showed pronounced (112) orientation, while films exhibiting more random orientation were obtained from pH buffered baths. Denser, smoother samples were obtained from non-pH buffered baths, though with no difference in film composition. As-deposited films exhibit low crystallinity and require recrystallization by annealing in H₂Se. Best devices, ∼ 9%, were obtained with CuInSe₂ films deposited from non-pH buffered baths.     

Nickel pulse reversal plating for image reversal of ultrathin electron beam resist

The effects of various pulse reversal plating parameters on the grain size and smoothness of Ni film on silver seed layers has been studied. The duty cycle, frequency, bath temperature and agitation methods have been tested. The objective was to form a thin continuous hard etch mask (20-30 nm of thickness) of Ni films for image reversal of thin film resist using electroplating. While nickel sulfamate solution without additives or brighteners has been used to plate Ni films, reactive ion etching (RIE) has been used to test the durability of the plated Ni films in fluorine plasma. It was found that pulse reversal plating with current intensity of 12 mA/cm², duty cycle of 90%, bath temperature of 45 °C, ultrasonic agitation of power 80 W, and 400 kHz wave frequency resulted in a plating rate as low as 0.2 nm/s. This plating rate made the control of the film thickness an easy task to achieve. This yielded to a smooth plated surface free from defects or voids, with 25 nm film thickness. Combining electron beam lithography with pulse reversal plating for image reversal and RIE offers the prospect of patterning patterns with the desired aspect ratio. Holes of 100 nm diameter, 250 nm period, and 300 nm depth are achieved using this process.     

Investigation of interface properties of Ti/Ni/Ag thin films on Si substrate

The interface structure and the adhesion of direct current (DC) sputtered Ti/Ni/Ag thin film metallization on n⁺Si substrate has been investigated. It is shown that beside the chemical preparation of the Si surface prior to sputtering also thermal annealing of sputtered metal structure has strong influence on the adhesion of sputtered layers to the silicon. Energy dispersive X-ray spectroscopy (EDS) analysis were performed on both, the delaminated layers and on the silicon surface to determine the exact delaminating interface, which was found to be between Si and Ti layer. Auger electron spectroscopy (AES) profile revealed no traces of contamination at Ti-Si interface. Measured high tensile residual stress, particularly in sputtered Ni layer (1.4-2 GPa) is found to reduce the metal stack adhesion.     

Effects of stress on the interfacial reactions of metal thin films on (0 0 1)Si

The influences of stress on the interfacial reactions of Ti and Ni metal thin films on (0 0 1)Si have been investigated. Compressive stress present in the silicon substrate was found to retard significantly the growth of Ti and Ni silicide thin films. On the other hand, the tensile stress present in the silicon substrate was found to enhance the formation of Ti and Ni silicides. For Ti and Ni on stressed (0 0 1)Si substrates after rapid thermal annealing, the thicknesses of TiSi₂ and NiSi films were found to decrease and increase with the compressive and tensile stress level, respectively. The results clearly indicated that the compressive stress hinders the interdiffusion of atoms through the metal/Si interface, so that the formation of metal silicide films was retarded. In contrast, tensile stress facilitates the interdiffusion of atoms. As a result, the growth of Ti and Ni silicide is promoted.     

Effects of substrate temperature on tin-doped indium oxide films deposited by dc arc discharge ion plating

Indium tin oxide (ITO) films were deposited on glass substrate at temperatures ranging from room temperature to 120 °C by the dc arc discharge ion plating technique. The electrical properties and crystallinity of ITO films were investigated. The resistivity of ITO films decreased with the increase of the substrate temperature in deposition, mostly due to increase in Hall mobility above 90 °C. The resistivity of ITO film obtained at temperature 120 °C was 1.33×10⁻⁴ Ω cm. The ITO films crystallized at the substrate temperature higher than 90 °C and the grain size estimated from the (2 2 2) peak in the direction parallel to the surface of the substrate became large with the increase of the substrate temperature. That the Hall mobility increased with the increase of the substrate temperature was speculated to be due to the increase of the grain size in the direction parallel to the surface.     

Epitaxial growth of Ni films sputter-deposited on a GaAs(001) surface covered with a MgO film

We studied the epitaxial growth of a Ni film prepared on a GaAs(001) substrate covered with a thin epitaxial MgO buffer film, assuming that this buffer film plays a key role in the epitaxial growth of the Ni film. The MgO and Ni films were deposited by radio-frequency magnetron sputtering of the MgO and Ni targets in pure Ar gas. First, a MgO film of thickness ranging from 78 to 4.4 nm was deposited on the GaAs(001) substrate at a temperature ranging from ambient temperature to 700 °C, and then, a 136-nm-thick Ni film was deposited on the MgO/GaAs substrate at a temperature range 300-500 °C. Using transmission electron microscopy and X-ray diffractometry, we showed that the MgO film grows with the epitaxial relationship MgO(001)[001]//GaAs(001)[001] on GaAs(001) at 500 °C, and that the structure of the Ni film depends on three factors: the MgO/GaAs substrate temperature, the MgO thickness, and the annealing condition of the MgO/GaAs substrate before the Ni deposition. In conclusion, we proved that the Ni film grows with the epitaxial relationship Ni(001)[001]//MgO(001)[001]//GaAs(001)[001] on MgO/GaAs with the 4.4-nm-thick MgO film when the MgO/GaAs substrate is annealed in situ at room temperature before the Ni deposition and maintained at 300 °C during the Ni deposition.     

Comparative study on the characteristics of network and continuous Ni films

Ni films were deposited on anodic aluminum oxide (AAO) and SiO₂/Si(100) substrates at 300 K by direct current magnetron sputtering with the oblique target. The film thickness was 80 nm, 160 nm and 260 nm. The films grown on AAO substrates have a network structure while those deposited on SiO₂/Si(100) substrates are continuous. The network film consists of granules and is formed by granule connection. The granule consists of many fine grains. The granule size increases with increasing film thickness. The 80 nm-thick network film has a honeycomb-like structure. The continuous films grow with a columnar structure and the transverse size of columnar grains increases with increasing film thickness. All the network films show a Ni(111) diffraction peak while the 160 nm- and 260 nm-thick continuous films exhibit the Ni(111) and Ni(200) diffraction peaks. The network films have higher coercivity and residual magnetization ratio compared with the continuous films. The coercivity and the residual magnetization ratio increase with increasing film thickness for the network films while they are almost independent of the film thickness for the continuous films. A temperature dependence of the resistance within 5-200 K reveals that the 80 nm-thick network Ni film exhibits markedly a minimal resistance at about 40 K. A logarithmic temperature dependence of the conductance is verified at temperatures below 40 K. The temperature coefficient of resistance is smallest for the 80 nm-thick network film and is largest for the 260 nm-thick continuous film.     

Structure and tribological properties of Ag films deposited at low temperature

The effects of substrate temperature on the structure and tribological properties of Ag films deposited at low temperatures (LT, 130-217 K) by arc ion plating (AIP) have been studied. The structure and morphology of the Ag films were analyzed by X-ray diffraction (XRD), transmission electron microscopy (TEM) and field emission scanning electron microscope (FESEM). The results showed that there exist (1 1 1) and (2 0 0) preferred orientation transitions for decreasing temperature at different bias voltages. The tribological properties were evaluated by a ball-on-disk tribometer and wear tracks were analyzed by means of scanning electron microscopy (SEM). The results show that substrate deposition temperature significantly affected the wear of LT Ag films. For each bias voltage studied, the film showing the highest wear rate was deposited at the lowest temperature and the film with the lowest wear rate, (significantly lower than room temperature (RT) deposited Ag films), was deposited at a temperature between the highest and the lowest temperatures examined. The wear mechanism was discussed in terms of lubrication effect of film material transferred to the counterpart and its dependence on the microstructure of the original deposited film.     

Metallization of Kevlar fibers with gold

Electrochemical gold plating processes were examined for the metallization of Kevlar yarn. Conventional Sn(2+)/Pd(2+) surface activation coupled with electroless Ni deposition rendered the fibers conductive enough to serve as cathodes for electrochemical plating. The resulting coatings were quantified gravimetrically and characterized via adhesion tests together with XRD, SEM, TEM; the coatings effect on fiber strength was also probed. XRD data showed that metallic Pd formed during surface activation whereas amorphous phases and trace amounts of pure Ni metal were plated via the electroless process. Electrodeposition in a thiosulfate bath was the most efficient Au coating process as compared with the analogous electroless procedure, and with electroplating using a commercial cyanide method. Strongly adhering coatings resulted upon metallization with three consecutive electrodepositions, which produced conductive fibers able to sustain power outputs in the range of 1 W. On the other hand, metallization affected the tensile strength of the fiber and defects present in the metal deposits make questionable the effectiveness of the coatings as protective barriers.     

Efficacy of Novel Electroless Plating Process for Dense Pd/Cr2O3/PSS Membrane Fabrication

This work addresses the role of chromia diffusion barrier on the combinatorial plating characteristics of Pd plating baths during fabrication of dense Pd/Cr₂O₃/porous stainless steel (PSS) composite membranes and is compared with those obtained during fabrication of Pd/PSS membranes. Cr₂O₃ was deposited by electroplating technique followed with oxidation at 700°C and Pd films were deposited using a novel Pd electroless plating process that provides optimal performance. Apart from providing similar process characteristics, the Pd/Cr₂O₃/PSS membrane provided 15.2% lower Pd film thickness in comparison with Pd/PSS membrane for similar pore densification values.     

Study of anodized Al substrate for electronic packaging

Al metal substrate with an anodic film separating the circuitry from the metal plate was developed by the means of anodization in this study. It was shown that an anodic film around 20–30 m thickness possessed the better properties, the resistivity was greater than 10¹⁴ cm, the dielectric constant was about 7 and the breakdown voltage exceeded 1000 V, which could satisfy the needs of the packaging. Electroless copper plating was attempted to complete the metallization of the anodized Al substrate, on which a fine Cu deposit could be obtained when the anodic film was sealed in a bath containing Ni, F ions.     

Production and characterization of boride layers on AISI D2 tool steel

AISI D2 is the most commonly used cold-work tool steel of its grade. It offers high hardenability, low distortion after quenching, high resistance to softening and good wear resistance. The use of appropriate hard coatings on this steel can further improve its wear resistance. Boronizing is a surface treatment of Boron diffusion into the substrate. In this work boride layers were formed on AISI D2 steel using borax baths containing iron-titanium and aluminium, at 800 °C and 1000 °C during 4 h. The borided treated steel was characterized by optical microscopy, Vickers microhardness, X-ray diffraction (XRD) and glow discharge optical spectroscopy (GDOS) to verify the effect of the bath compositions and treatment temperatures in the layer formation. Depending on the bath composition, Fe₂B or FeB was the predominant phase in the boride layers. The layers exhibited “saw-tooth” morphology at the substrate interface; layer thicknesses varied from 60 to 120 μm, and hardness in the range of 1596-1744 HV were obtained.     

A facial microwave-assisted polyol activation process for fabrication of Ni@PMMA microspheres

A simple and efficient activation process was conducted by deposition of palladium (Pd) nanoparticles on PMMA surface using a microwave-assisted polyol method with ethanol used as the reductant. The newly synthesized Pd nanoparticles were utilized as an activator for electroless nickel deposition. TEM images revealed that Pd nanoparticles of size 4-6 nm are formed evenly over the PMMA surface. A tight, smooth and continuous Ni plating layer was coated on these Pd nanoparticle activated PMMA microspheres. In contrast, a rough and discontinuous Ni film was obtained for the sample activated with a conventional sensitization/activation procedure.