Hexagonal diamond formation on steel substrates by negative bias microwave plasma enhanced chemical vapor deposition

This paper reports for the first time the synthesis of hexagonal diamond thin films on high-speed steel substrates by multi-mode microwave plasma enhanced chemical vapor deposition. Before deposition of the films, the substrate surface was treated by scratching with diamond powder. The deposited films were characterized by X-ray diffraction (XRD), Raman spectroscopy and scanning electron microscopy. The XRD patterns of (100) and (101) planes and the Raman peaks at ~ 1317-1322 cm^− 1 were observed, confirming the formation of hexagonal diamond phase in the prepared films. The effects of voltage bias on the phase formation, microstructure and hardness of the films were also studied by setting the voltage to 0, − 70, − 150 and − 190 V. The highest hardness of 23.8 GPa was found in the film having clusters of size about 550 nm deposited under a bias voltage of − 150 V. These clusters were built up of grains of size about 14 nm.     

Influence of Si content and growth condition on the microstructure and mechanical properties of Ti-Si-N nanocomposite films

Thin films of Ti-Si-N have been prepared by ion beam assisted deposition (IBAD) from two Ti and Si targets. The silicon concentration in the deposited coatings is varied between 0 and 23.7 at.%. The influence of Si content and growth conditions on the microstructure and mechanical properties were investigated using XPS, AFM, XRD and nanoindenter. These nanocomposite coatings exhibit improved mechanical properties in comparison with TiN deposited under the same condition. The hardness measured by nanoindentation reached 42 GPa in Ti-Si-N films containing 11.32 at.% of Si, whereas TiN films only had a value of about 18 GPa. AFM showed that the finest grain size of Ti-Si-N appeared to be 5 nm when Si content was 11.32 at.%. From XPS and XRD results, the microstructures of the high hardness samples were found to consist of nanocrystal TiN grains and amorphous Si₃N₄.     

Technology of metal oxide thin film deposition with interruptions

The idea to obtain metal-oxide films with small grain size is to use a special regime of thin film deposition by r.f. sputtering of pure metal or metal oxide targets. This regime includes the deposition of thin films with one or several interruptions during the deposition process. WO₃ films were r.f. sputtered onto pure and oxidized silicon wafers. Four types of films were prepared, i.e. using continual deposition, one, two and three interrupted depositions with an actual deposition time of 40 min. The interruption time changed from 0.5 min to 5.0 min for the different samples. It was found that the total thickness of WO₃ films decreased with the increase of the number of interruptions and the increase in interruption time. Phase composition and features of surface morphology of the films deposited and annealed in the temperature range from room temperature to 900 °C have been investigated by XRD and AFM, respectively. It is shown that grain size in the metal oxide films decreased essentially with the increase of the number of interruption during the deposition process.     

Electrophoretic deposition of conjugated polymer: Deposition from dilute solution and PEDOT coating effect

It has been shown that the films of a soluble conjugated polymer poly[(9,9-dioctyl-2,7-divinylene fluorenylene)-alt-{2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene}] for electronic devices can be prepared by the electrophoretic deposition with polymer suspensions derived from dilute polymer solutions which are so dilute that the conventional spin-coating technique is not applicable. For example, a 100 nm-thick film can be prepared on an indium-tin-oxide (ITO) electrode from a suspension from solution containing 0.1 g/l of the polymer. The thickness of the polymer film deposited is found to be almost proportional to the concentration of the polymer, and the linearity down to 5.0 × 10^?3 g/l is confirmed. On the other hand, it has been found that coating the ITO electrode with poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) salt results in low and nonlinear deposition rate.     

Preparation and corrosion behavior of electrodeposited Ni–TiN composite coatings

Ni–TiN composite coatings were successfully prepared by direct current (DC), pulse current (PC) and ultrasonic pulse current (UPC) deposition methods. The morphology, mechanical properties and the corrosion behavior of Ni–TiN composite coatings were investigated using atomic force microscope (AFM), scanning electronic microscope (SEM), X-ray diffraction (XRD) and gravimetric analysis. The results show that the Ni–TiN composite coatings synthesized by UPC deposition method possess a compact and exiguous surface morphology. The XRD results demonstrate that the average grain diameter of Ni and TiN in composite coating prepared by UPC deposition is 52.6 and 35.7 nm, respectively. In the corrosion tests, the coating prepared by UPC deposition exhibits the best corrosion resistance, whereas the coating fabricated by DC deposition suffers the most serious damage.     

Deposition of dense and smooth Ti films using ECR plasma-assisted magnetron sputtering

We report high quality Ti films grown in a novel electron cyclotron resonance (ECR) plasma-assisted magnetron sputtering (PMS) deposition system. The films are compared with films deposited by conventional direct current (DC) magnetron sputtering. Using ECR-PMS, the argon plasma bombardment energy and Ti film deposition rate can be controlled separately, with the substrate bias voltage under feedback control. Results from SEM, AFM, XRD and PAS (scanning electron microscopy, atomic force microscopy, X-ray diffraction and positron annihilation spectroscopy) show that the properties of Ti films prepared by ECR-PMS are greatly improved compared with conventional sputtering. SEM and AFM confirmed that ECR-PMS Ti films have a dense, smooth, mirror-like surface. Increasing the substrate bias of the ECR plasma from − 23 V to − 120 V while keeping a fixed sputtering bias voltage of − 40 V, the intensity of the (100) reflection of Ti film was a little strengthened, but (002) remained strongly preferred orientation. The XRD peak broadening of ECR-PMS Ti films is more than for conventional magnetron sputtering, due to grain refinement induced by Ar ion bombardment. Doppler broadening of PAS analysis reveals that the Ti films have fewer vacancy defects compared with films prepared by the conventional magnetron.     

Orientation of nanowires consisting of poly(3-hexylthiophene) using strong magnetic field

Nanowires consisting of regioregular poly(3-hexylthiophene) (P3HT) as a conducting polymer were prepared using p-xylene. Magnetic processing of the nanowires was carried out using two superconducting magnets with horizontal (B_max = 8 T) and vertical (B_max = 10 T) directions. The formation of the nanowires was confirmed by atomic force microscopy (AFM) measurement. The results from the AFM images and the polarized absorption spectra on glass plates indicated that the nanowires partly oriented themselves with their long axes, which are parallel to the π–π stacking direction, being perpendicular to the magnetic field. The magnetic orientation is most likely ascribed to anisotropy in the magnetic susceptibilities of the ordered P3HT in the nanowires.     

High purity boron nitride thin films prepared by the PDCs route

Hexagonal boron nitride (h-BN) thin films (< 10 μm) were successfully obtained on various substrates (graphite-standard and HOPG, quartz and SiC) using the preceramic polymer route. Thin films were formed using precursor solutions of poly(2,4,6-trimethylamino)borazine (polyMAB) as a source of BN. Various preparation conditions were used (i.e. solvent, precursor nature and concentration, substrate and deposition method) and their impact on final BN film quality measured. Surface morphology was observed by Scanning Electronic Microscopy (SEM) and Atomic Force Microscopy (AFM). Presence of BN material was confirmed by infrared and Raman spectroscopies and the structure observed by High Resolution Transmission Electronic Microscopy (HRTEM). The chemical composition of samples analyzed by X-ray Photoelectron Spectroscopy (XPS) gives a B/N ratio close to 1. Boron nitride films were also prepared using borazine (B₃N₃H₆) as precursor. Initial results are presented and compared with those obtained from polyMAB solutions.     

Self-organized gold nanostructures on laser patterned PET

Irradiation of polyethyleneterephtalate (PET) with linearly polarized light from a pulsed 248 nm KrF laser with 6000 pulses per area and fluences between 2.0 and 8.4 mJ·cm^? 2 resulted in formation of coherent ripple patterns with a lateral periodicity in the order of laser light wavelength and structure depth of several 10 nm. The structure period could be controlled by variation of the incidence angle of the laser beam. Subsequently, thin gold layers were deposited onto the laser patterned PET surface either by sputtering and evaporation. The resulting structures were analyzed by atomic force microscopy (AFM) and focused ion beam cuts in combination with scanning electron microscopy (FIB-SEM). Evaporation leads to a continuous metal coverage copying the nanostructured polymer surface, while sputtering leads to formation of isolated nano-wires on the ridge of the laser-induced ripples. The width of the gold nano-wires could be tailored by the ripple periodicity formed before the deposition process.     

A comparative study of the electrochemical deposition of molybdenum oxides thin films on copper and platinum

Molybdenum oxides thin films electrochemical deposition was performed using solutions of peroxo-polymolybdate at pH 2.3 and ammonium molybdate at pH 5.5 as precursors and smooth copper and platinum as supports. The deposition has been carried out at constant potentials in the range of −600 to −800 mV vs. Ag/AgCl (sat. KCl). The thin films deposited on copper were then heated at 350 and 450 °C in argon. In the case of thin films deposited from ammonium molybdate and heated at 450 °C, the XRD spectra reveal, along with MoO₂, the presence of Cu₆Mo₅O₁₈ phase. For the thin films prepared from peroxo-polymolybdate and subjected to the same heat treatment, the only XRD phase present was MoO₂. Thermogravimetric (TG) analysis was performed on samples prepared by scraping away the thin films (molybdate precursors) from the copper support. Before heat treatment, the AFM images of the as-deposited thin film reveal a granular morphology, with diameters in the 20–80 nm range.     

Fabrication of regioregular poly(3-hexylthiophene) field-effect transistors by dip-coating

We report the influence of dip-coating speed and concentration of the polymer solution on the characteristics of field-effect transistors (FETs) fabricated in the bottom-contact structure with regioregular poly(3-hexylthiophene) (RR-P3HT) as the active semiconducting material. For each concentration of the polymer in solution, there is an optimum dip coating speed for film deposition with highest field effect mobility; for example, with chloroform as solvent the optimum speed is 0.5 mm/min for a solution containing 1.0 mg/ml and 1.0 mm/min for a solution containing 2.5 mg/ml. Based upon AFM studies of the resulting film morphology, we conclude that the formation of a “rod-like” morphology is the origin of the improved carrier transport in the FET channel.     

Effect of structure and morphology on photocatalytic properties of TiO2 layers

TiO₂ layers were deposited by reactive pulse magnetron sputtering at a substrate temperature of 400 °C on float glass. The total pressure during the deposition was varied between 0.3 and 3 Pa for modification of the surface morphology.The morphology of 500 nm thick layers was analyzed by AFM and SEM investigations. X-ray diffraction investigations reveal that the structure consists mainly of anatase and small contents of rutile phase. With increasing total pressure from 0.3 to 1.2 Pa the average roughness value (Ra) is increased from 4.5 to 8.0 nm. The lateral grain size on layer surface determined by AFM amounts to between 75 and 100 nm. By a further increase of total pressure to 2 Pa and 3 Pa the formation of a nanocrystalline microstructure with grain size less than 50 nm can be recognized. Simultaneously the Ra value is reduced to 2.4 nm.The effect of structure and morphology on photocatalytic activity of the layers was determined by the decomposition of methylene blue solution under UV-A radiation. For total pressures between 0.3 and 1.2 Pa the photocatalytic activity is drastically enhanced by increasing roughness and therefore higher free surface area for the photocatalytic reaction. In contrast the formation of nanocrystalline structure at higher total pressures of 2 and 3 Pa is linked with a deterioration of photocatalytic properties. This effect can be explained mainly by the high defect density of these layers and therefore high recombination rates for electron hole pairs.     

Magnetite nanoparticles by organic-phase synthetic route for carbon nanotube growth

In the present study, monodisperse Fe₃O₄ nanoparticles with diameters ranging from 10 nm to 25 nm were synthesized using a simple organic-phase synthetic route and these monodispersed nanoparticles were then used as catalyst for seed growth of carbon nanotube. Fe₃O₄ nanoparticles were reduced to iron nanoparticles assembly by Argon mixed with 5% Hydrogen gas at 400 °C and then it was examined by atomic force microscopy (AFM), thermomechanical analysis (TMA) and powder diffraction X-ray spectroscopic techniques. XRD indicates that iron clusters are bcc in nature and AFM image shows that the iron nanoparticles assemblies are 50–65 nm in size. To control the agglomeration of iron nanoparticles, nanoporous hybrid support material of Al₂O₃ and SiO₂ was used. However, this matrix also fails to stop the agglomeration of iron nanoparticles mainly due to the inhomogeneous distribution of pore diameters. TMA analysis of iron clusters shows a temperature-dependent morphology, therefore, the CNTs growth temperature critically ascertain the nature and structure of CNTs.     

Co-deposition process of RF-Sputtering and RF-PECVD of copper/carbon nanocomposite films

Nanoparticle copper/carbon composite films were prepared by co-deposition of RF-Sputtering and RF-PECVD method from acetylene gas and copper target. We investigate deposition process in the region where by changing pressure, the process converts to physical sputtering mode in constant power regime and at a critical pressure between 1.5 to 3 Pa. The estimated value of mean ion energy at this critical point of pressure is close to threshold energy of physical sputtering of copper atoms by acetylene ions. By utilizing this property and by setting initial pressure from 1.3 to 6.6 Pa, nanoparticles copper/carbon composite films were grown with different copper content. The Copper content of our films was obtained by Rutherford Back Scattering (RBS) and it varied from 2% to 97%. The copper content of the surface was obtained by X-ray Photoelectron Spectroscopy (XPS). The results of XPS at different stages of the growth and copper oxidization confirm our suggested mechanism of deposition. Atomic force microscopy (AFM) image and X-ray diffraction (XRD) indicated that copper nanoparticles were formed in our films.     

The wide band gap of highly oriented nanocrystalline Al doped ZnO thin films from sol–gel dip coating

Undoped and Al doped ZnO thin films were prepared on glass substrate by sol–gel dip coating from PVP-modified zinc acetate dihydrate and aluminium chloride hexahydrate solutions. The XRD patterns of all thin films indexed a highly preferential orientation along c-axis. The AFM images showed the average grain size of undoped ZnO thin film was about 101 nm whereas the smallest average grain size at 8 mol% Al was about 49 nm. The values of direct optical band gap of thin films varied in the range of 3.70–3.87 eV.     

In situ AFM study of the electrochemical deposition of polybithiophene from propylene carbonate solution

Early stages of galvanostatic deposition of polybithiophene onto highly oriented pyrolytic graphite (HOPG) from propylene carbonate solution were investigated using electrochemical atomic force microscopy (ECAFM). The polymer film thickness was evaluated in situ using surface modification with the AFM tip and was found to be proportional to the grafting charge Q and independent of the deposition current density i in the current density range from 0.1 mA/cm² to 2 mA/cm². The first stage of the deposition was the formation of polymer nuclei with an average height of ca. 1 nm; continuous film was formed at Q≥0.5 mC/cm². Even at the earliest stages, the polymer featured grain structure with the average grain size of ca. 50 nm. The presence of the crystalline phase in the films was demonstrated by the X-ray diffraction data.     

Size distribution of precipitated Ni clusters on the surface of an alkaline-treated LaNi5-based alloy

The size distributions of precipitated Ni clusters on the surface of a LaNi₅-based alloy immersed in alkaline solution (alkaline treatment) at 383 K for 0–110 min were precisely determined by combining superparamagnetic analysis and transmission electron microscopy (TEM) observations. The superparamagnetic analysis indicated that the diameters of the Ni clusters were smaller than ∼25 nm in all samples, while their average values increased approximately from 5 to 9 nm with increasing alkaline treatment time. The spatial distribution of the Ni clusters was successively observed by TEM, which agreed fairly well with the estimated size distribution by superparamagnetic analysis. Therefore, estimation of the actual size distribution of Ni clusters by superparamagnetic analysis was proved to be feasible. Based on the above results, a precipitation process for Ni clusters by alkaline treatment is proposed.     

Vapor phase polymerization of poly (3,4-ethylenedioxythiophene) on flexible substrates for enhanced transparent electrodes

Recently, conducting polymer thin films have been investigated as transparent electrodes in photovoltaic devices and organic light emitting diodes. Due to its relatively high conductivity and excellent transmission in the visible region, poly (3, 4-ethyelenedioxythiophene) (PEDOT) has been shown to be a viable option for such applications. Herein described is a method for the vapor phase polymerization (VPP) of transparent PEDOT thin film electrodes on flexible polyethylene naphthalate (PEN) substrates and the comparison of this VPP method with two current approaches to PEDOT deposition: solution-based in situ polymerization and spin coating a dispersion of PEDOT:PSS. Electrical conductivities and UV–vis transmittances were measured for films produced by each of these methods, with VPP PEDOT showing both the highest conductivity (approx. 600 S/cm) and transmittance (>94% at 550 nm). The surface morphologies of the films were compared using AFM and SEM imaging. The stability of these PEDOT films, stored under ambient conditions, was investigated by monitoring the conductivity and transmittance of the thin films over time.     

Morphological, structural, and mechanical characterizations of InGaN thin films deposited by MOCVD

Presented in this study are surface roughness, crystalline structure, and nanomechanical properties of InGaN thin films deposited under various growth temperatures, obtained by means of X-ray diffraction (XRD), atomic force microscopy (AFM), and nanoindentation techniques. The InGaN thin films with different In contents were deposited on sapphire substrates through a metal-organic chemical-vapor deposition (MOCVD) system. Changes in mechanical properties for InGaN thin films are discussed in conjunction with deposition temperature, surface morphology and crystalline structure. The XRD measurements showed that there was no phase separation of In as the In composition went from 25 at.% to 34 at.%. Moreover, both XRD and AFM showed larger grain and surface roughness in In_0.25Ga_0.75N thin films. Nanoindentation results indicate that hardness and Young's modulus both decreased as the indentation depth increased. The contact stress–strain relationships were also analyzed.     

Plasma polymer multilayers of organosilicones and their optical properties controlled by RF power

Hydrogenated amorphous carbon–silicon alloys were prepared from tetravinylsilane monomer using plasma-enhanced chemical vapor deposition at different powers (10–70 W). The optical properties of the plasma polymer films were analyzed by spectroscopic ellipsometry in the range 250–830 nm. The refractive index of pp-TVS films can be controlled by RF power, which for a wavelength of 633 nm ranged from 1.69 (10 W) to 2.08 (70 W). Alloys of selected optical properties were used to construct layered films with sharp interfaces. We could confirm that individual layers retain their optical properties in layered structures if the layer thickness is between 1 μm and 25 nm. Nanolayered and gradual films of controlled optical properties can be developed for nanolayered composites and optical devices.