Single-phase TiN Research Articles

Effect of Substrate Temperature on Structural, Electrical and Optical Properties of Sprayed Tin Selenide Thin Films Applicable for Photovoltaic Measurements

Thin films of Tin selenide (SnSe) have been prepared on glass substrates at different temperatures in the range of 250 °C–375 °C in steps of 25 °C for optimization were discussed. The deposited tin selenide thin films were characterized using X-ray diffraction analysis (XRD), Elemental dispersive X-ray analysis (EDAX), Scanning electron microscopy (SEM), Optical absorption, Photoluminescence (PL), Raman spectroscopy and electrical measurements. From XRD analysis a single-phase tin selenide thin film having orthorhombic crystalline structure with crystallite size of 17 nm to 62 nm were investigated. The surface morphology revealed the presence of uniformly distributed spherical grains of SnSe thin films without pores and voids. Optical absorption spectrum revealed a direct band gap of 1.15 eV and having very high absorption coefficient (˃104/cm) was calculated. The Raman scattering analysis confirmed the presence of B3g and Ag vibrational modes of SnSe thin films. PL studies revealed a strong luminescence peak near-band-edge (NBE) emission at 785 nm due to recombination of bound excitons. Photoconductivity characteristics of SnSe thin films were due to the existence of continuous distribution of localized states in the band gap data. Thus tin selenide thin films were used as an absorber layer in the photovoltaic application.

Sulfurization temperature dependent properties of tin mono-sulfide thin films

Tin mono-sulfide thin films were prepared using a two-step process consisting of DC sputtered deposition of Sn precursors over glass substrate held at 150 oC, followed by sulfurization for 1 hour at different temperatures ranging from 250 oC to400 oC. The influence of the sulfurization temperature on resultant films was studied in terms of its structure, morphology and opto-electronic properties. X-ray diffraction study revealed that the films sulfurized at lower temperature (~250 oC) had prominent SnS2 phase in addition to SnS. A single-phase tin mono-sulfide planes corresponding to orthorhombic structure has been observed at 300 oC and found to be highly crystalline at 350 oC. Further, three distinct Raman modes observed at 95, 190 and 218 cm-1 for Sn precursors sulfurized at 350 oC, strongly supporting the formation of single phase SnS. The optimized SnS film showed a direct band gap of 1.35 eV with an absorption coefficient of 5 x 104 cm-1. The valence states of Sn (+2) and S (-2) determined from X-ray photoelectron spectroscopy analysis for Sn precursors sulfurized at 350 oC, indicating the existence of SnS. These films had stoichiometric atomic ratio of Sn/S ~ 1 with surface roughness of 20 nm. All the films have shown p-type conductivity and the Sn precursors sulfurized at 350 oC exhibited relatively high conductivity of 0.947 x 10-2 (Ω cm)-1. The optoelectronic properties of SnS films reported in the present work would be highly suitable for device fabrication and promising as an alternative absorber for thin film solar cells. Copyright © 2017 VBRI Press.

Substrate Effects on Crystal Phase in Atomic Layer Deposition of Tin Monosulfide

Obtaining single-phase tin monosulfide (SnS) films at low temperatures is challenging since cubic (π-SnS) and orthorhombic (α-SnS) polymorphs have similar energies of formation and grow under similar conditions. Here, we show that in atomic layer deposition (ALD) of polycrystalline SnS using tin(II) acetylacetonate and H2S precursors, the substrate surface greatly influences the SnS phase evolution. For example, a silicon (100) substrate, with a highly hydroxylated surface, favors the growth of α-SnS. Meanwhile, ozone treatment or preannealing of the same substrate leads to mainly π-SnS. Just a few ALD cycles of another oxide or sulfide can even more substantially alter the outcome. Substrates that favor α-SnS growth typically produce initially enhanced growth rates, while those promoting π-SnS are partially surface-poisoned by the acetylacetonate precursor ligands. Growth of either polymorph is self-sustained after its initiation, and the sustaining factor appears to be the surface–ligand interaction; π-SnS preferentially evolves on substrates and π-SnS surfaces that are rich in highly reactive dangling bonds, while chemically inert substrates and α-SnS surfaces promote α-SnS. While lattice matching is less central, the role of ligand bonding in SnS ALD also helps explain the previously reported phase dependence on growth temperature and H2S precursor dose and shows promise for area-selective ALD of SnS.

The Effect of the Precursor Molarities on the Composition, Microstructure and Optical Properties of Tin Sulphide Films Obtained from S-SILAR Technique

The tin sulphide films obtained from chemical routes normally have two or more mixed phases (SnS, SnS2 and Sn2S3). The present paper reports a holistic approach to synthesize nearly stoichiometric, single phase tin sulphide (SnS) thin films by simplified SILAR (S-SILAR) technique without using any complexing agents. The material wastage due to precipitation was also reduced significantly. The cationic and anionic solutions were taken in 2:1 ratio. The solution molarity was found to have a strong bearing on the chemical composition, structural and optical properties of the films. The terminal thickness of the films was about 800 nm. The XRD patterns of the films confirmed that the films obtained from high molarity solutions were almost completely orthorhombic with preferred orientation along (040) plane without any mixed phases. The post-deposition heat treatment was found to be beneficial for the fine tuning of stoichiometry. The S/Sn ratio obtained for annealed films with 0.01 M, 200 cycles combination was 1.07. The optical absorption was substantial in visible and NIR regime with excellent photo-absorption coefficient. The films obtained from solutions with higher molarity were found to have a direct optical bandgap of 1.5 eV, which is highly desirable for NIR photodetectors and photovoltaic applications.

Electrodeposition of Single Phase SnS Thin Films: Effect of Electrolytic Bath Temperature on the Final Film Properties

In this article, the electrodeposition of single-phase tin monosulfide (SnS) films at different electrolytic bath temperatures is studied. The electrodeposition was carried out potentiostaticaly onto transparent conductive substrates (fluorine-doped tin oxide, and indium tin oxide on a glass substrate) from an acidic solution of SnSO4 and Na2S2O3 as tin and sulfur precursors, respectively. The films were characterized through different techniques: field-emission scanning electron microscopy, energy dispersive X-ray analyses, X-ray diffraction measurements, profilometry, Raman spectra, UV-vis measurements, electrochemical impedance spectroscopy and linear sweep photovoltammetry. The films obtained were stoichiometric and no other phases different from SnS were evidenced. A change in the morphology from cubic-like to sheet-like was observed with an increase of bath temperature, which was reflected in the texture coefficient obtained from X-ray diffraction analyses. The bandgap of the films was obtained using a direct absorption edge in the Tauc plots. A decreasing bandgap with electrodeposition temperature was observed, which is attributed to an improvement in the crystallinity of the films. Mott-Schottky plots and linear sweep photovoltammetry measurements confirmed that the films are p-type semiconductors. An increase in the photocurrent of the photoelectrodes was observed with the electrolytic bath temperature, which is attributed to the change of SnS morphology with the electrodeposition temperature.

Synthesis of Single Phase Tin(II) Oxide Nanoparticles by Microwave-Assisted Hydrothermal Technique

This paper presents a novel microwave-assisted hydrothermal technique for synthesizing tin(II) oxide nanoparticles. This technique can be used for producing large quantities of homogeneous nanoparticles in a short time. The effect of the solution molarity, final pH, hydrothermal processing time and microwave power were studied. The tin(II) oxide structure verified from XRD and the mean crystallite size was evaluated to be about 5 nm using the Debye-Scherrer formula on the most intense peak. The particle size was measured from STM pictures in the range between 4-5 nm. For different samples, UV-Vis spectroscopy showed the absorption peak due to tin(II) oxide at about 240 nm and an exitonian peak at about 280 nm that shifted with respect to solution molarity, final pH, hydrothermal processing time and microwave power. The photoluminescence spectroscopy (PL) results showed the emission peaks in the visible spectrum range. The results showed that synthesized SnO nanoparticles have a direct bandgap equal to about 2.5 eV, an Urbach energy of about 2.7 eV and activation energy of 47.75kJ/mol.

Chemical vapor deposition of TiN on transition metal substrates

The growth of chemical vapor deposited TiN from a reaction gas mixture of TiCl4, N2 and H2 was investigated on three different transition metal substrates: Fe, Co and Ni at deposition temperatures ranging from 850°C to 950°C. The interactions between the substrate metals and the gas phase were investigated using thermodynamic calculations. The TiN coatings were characterized by scanning electron microscopy, scanning transmission electron microscopy, X-ray diffraction, energy dispersive X-ray spectroscopy and transmission Kikuchi diffraction.Chemical vapor deposition (CVD) of TiN on Co substrates resulted in dense, columnar coatings of single phase TiN. The activation energy for TiN deposition on Co was determined to be 90kJ/mol. CVD of TiN on Fe substrates caused severe substrate corrosion by the formation of gaseous FeClx. Due to the substrate corrosion, the activation energy could not be determined. Furthermore, it was found that CVD of TiN on Ni substrates produced a phase mixture of TiN and Ni3Ti. Formation of Ni3Ti could be minimized by decreasing the H2 partial pressure and increasing the N2 partial pressure. Deposition on Ni yielded two different activation energies, 40kJ/mol in the temperature interval 850°C to 900°C and 165kJ/mol in the interval 900°C to 950°C. This is an indication of two different types of process control, which were identified as Ni diffusion into the growing film and a gas phase processes. The results of the present study showed that CVD of TiN on a cemented carbide using Fe and Ni in the binder phase, must be optimized in order to avoid corrosion or unwanted phases. Methods to achieve this are presented in this paper.

Superimposed high power impulse and middle frequency magnetron sputtering: Role of pulse duration and average power of middle frequency

The low deposition rate of the high power impulse magnetron sputtering (HiPIMS) somewhat limits its commercial applications in thin film and coating industries. In this work, an effective way to improve the deposition rate of TiN film by superimposing the middle-frequency (MF) pulses during off-time of HiPIMS pulsing was discussed. Superimposition of HiPIMS and MF fabricated TiN films with relatively smooth surface. All samples were found to have a single phase TiN according to the chemical composition and crystallographic analyses. The highest film hardness of ~31GPa, elastic modulus of 313GPa, and a density of 5.35g/cm3 were obtained in the sample grown at a MF pulse duration of 150μs in each superimposed cycle. The higher the deposition rate was achieved with longer MF pulse duration. This superimposition technique successfully improved the power-normalized deposition rate from 4.5 to 17.2nm/kW·min without significantly declining the mechanical properties and adhesion quality of deposited films. The role of MF pulse duration and average MF power were further studied in this work. It can be concluded that the MF pulse duration played a more significant role and showed a dominant influence on the plasma characteristics and resulting properties of deposited TiN films.

SnS thin films grown by sulfurization of evaporated Sn layers: Effect of sulfurization temperature and pressure

SnS thin films were grown by sulfurization of Sn layers evaporated by electron beam. The effect of sulfurization parameters, such as temperature and pressure, on the properties of tin sulfide layers has been investigated. Ar pressure used during the sulfurization has a strong impact on the development of a proper SnS/Mo back interface. However, the sulfurization temperature is the parameter that regulates the formation of an orthorhombic single phase SnS thin film with the optimum properties to be used as absorber for solar cell devices. Sulfurization temperature of 220°C for 240min led to the formation of single phase tin sulfide layers. Direct band gap energy about 1.2eV has been determined.

Single phase tin sulfide films prepared by one-bath electrodeposition

Single phase SnS films were potentiostatically electrodeposited on ITO-coated glass substrates in an aqueous solution containing 10 mM SnSO4 and 50 mM Na2S2O3 at a pH of 2.7 while varying the deposition potential, bath temperature, and stirring. Contrary to room temperature deposition, agitation using a magnetic stirrer in the electrodeposition process at 45 °C significantly promoted the deposition rate and enlarged the crystal size of the SnS compounds. The structural, morphological, and optical properties of the SnS films, which had nearly stoichiometric compositions, were characterized. All of the synthesized SnS films were determined to be p-type semiconductor material by photoelectrochemical testing under illumination. The thicker samples obtained with stirring exhibited an optical band gap of ~1.02 eV, which is almost identical to the theoretical value. The p–n junction heterostructures of the ITO/SnS/ZnO/In were fabricated and their rectifying behaviors were characterized under dark condition.

Production of titanium nitride nanopowder from titanium hydride based on synthesis in thermal plasma

The synthesis of TiN nanopowder from titanium hydride in thermal plasma generated in DC arc plasmatron is investigated experimentally. It is shown that a single-phase TiN nanopowder can be produced within a two-stage process consisting of plasma synthesis and separation of powdered product by means of sedimentation. The yield of nanopowder is up to 90%.

Temperature effect over structure and photochemical properties of nanostructured SnO2 powders

AbstractWe successfully synthesized tin dioxide nanoparticles with polyhedral morphology via an ethylene glycol assisted sol-gel approach. The structural characteristics of three tin dioxide samples were investigated after being thermally treated at 400°C, 600°C and 800°C. X-ray diffraction (XRD) patterns clearly show the formation of single phase tin dioxide nanoparticles, with crystallite size of 6–20 nm, in good correlation with Fourier transform infrared (FTIR) spectra. Transmission electron microscopy (TEM) analysis confirms the formation of 6nm polyhedral nanoparticles for the 400°C sample. Ultraviolet-visible (UV-Vis) and photoluminescence (PL) spectra suggest a high concentration of oxygen vacancies. The oxygen vacancy concentration increases with temperature, due to the combined action of the formation of VO and the energetic O compensation. X-ray photoelectron spectroscopy (XPS) analysis also confirms the formation of single phase tin dioxide and the presence of oxygen vacancies in good agreement with UV-VIS and PL data.

Features of the structure of TiN films after irradiation with nitrogen

In this work, we study the structure of submicron titanium-nitride films after surface treatment with a nitrogen-ion beam. It is ascertained that nitrogen-ion beams affect two-phase TiN-Ti films thus transforming them into single-phase TiN.

Electrochemical behavior of superhard nanocomposite coatings of TiN/Si3N4 prepared by reactive DC unbalanced magnetron sputtering

Nanocomposite coatings of TiN/Si3N4 are new generation superhard coatings having hardness greater than 40GPa. Apart from high hardness, these coatings exhibit outstanding properties such as improved wear resistance and high oxidation resistance. These coatings also retain their hardness even after heating in air at higher temperatures. The present study reports electrochemical behavior of superhard nanocomposite coatings of TiN/Si3N4 in 3.5% NaCl solution. The nanocomposite coatings with varying silicon contents have been prepared on steel substrates by reactive direct current unbalanced magnetron sputtering. Single-component TiN and Si3N4 coatings have also been included in the investigation. The electrochemical measurements were performed by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The corroded samples were characterized using scanning electron microscopy and energy dispersive X-ray analysis. The nanocomposite coatings exhibited better corrosion resistance than single-phase TiN coatings. Nyquist and Bode plots obtained from the EIS measurements for bare steel substrate, single-component TiN and nanocomposite coatings were used for evaluating the corrosion behavior. The charge transfer resistance and the double layer capacitance were also calculated using EIS data.

Highly Selective Chemical Vapor Deposition of Tin Diselenide Thin Films onto Patterned Substrates via Single Source Diselenoether Precursors

The distorted octahedral complexes [SnCl4{nBuSe(CH2)nSenBu}] (n = 2 or 3), (1) and (2), obtained from reaction of SnCl4 with the neutral bidentate ligands and characterized by IR/Raman and multinuclear (1H, 77Se{1H} and 119Sn) NMR spectroscopy and X-ray crystallography, serve as very effective single source precursors for low pressure chemical vapor deposition (LPCVD) of microcrystalline, single phase tin diselenide films onto SiO2, Si and TiN substrates. Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) imaging show hexagonal plate crystallites which grow perpendicular to the substrate surface in the thicker films, but align mostly parallel to the surface when the quantity of reagent is reduced to limit the film thickness. X-ray diffraction (XRD) and Raman spectroscopy on the deposited films are consistent with hexagonal SnSe2 (P3̅m1; a = b = 3.81 Å; c = 6.13 Å), with strong evidence for preferred orientation of the crystallites in thinner (0.5–2 μm) samples, consistent with crystal plate growth parallel to the substrate surface. Hall measurements show the deposited SnSe2 is a n-type semiconductor. The resistivity of the crystalline films is 210 (±10) mΩ cm and carrier density is 5.0 × 1018 cm–3. Very highly selective film growth from these reagents onto photolithographically patterned substrates is observed, with deposition strongly preferred onto the (conducting) TiN surfaces of SiO2/TiN patterned substrates, and onto the SiO2 surfaces of Si/SiO2 patterned substrates. A correlation between the high selectivity and high contact angle of a water droplet on the substrate surfaces is observed.

Ultrasonically Assisted Synthesis of Tin Sulfide Nanorods at Room Temperature

A simple ultrasonic method was developed to synthesize rod-like SnS nanocrystals, using tin chloride and thioacetamide as starting materials, ethanolamine and water as solvents. The as-obtained nanostructures were characterized by X-ray diffraction (XRD) study, energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Ultraviolet-visible spectrophotometry (UV). From the XRD pattern, the reflection peaks of the as-obtained samples can be indexed to the orthorhombic structure with lattice constants a = 3.99, b = 4.34, c = 11.20 Å , which are very consistent with the values in the standard card of SnS phase (JCPDS No. 39-0354). No characteristic peak was observed for other impurities such as SnO2 and SnS2, implying the formation of single-phase tin monosulfide. The quantification calculation shows the ratio of Sn/S to be 51.30/48.70 via the EDS analysis. These data clearly indicate that the as-prepared rod-like nanostructures are exactly SnS. TEM results show that, the SnS nanorods have length about 100nm and width less than 30nm. The direct and indirect band gaps of the SnS nanorods are determined to be 1.53 eV and 1.34 eV, respectively. The band gaps of the as-obtained SnS nanorods showed blue shifts due to the quantum size effects. The ultrasonic condition is believed to be critical for the formation of SnS with pure phase. For it provides the energy to form rod-like nanostructures and helps preventing the hydrolysis of Sn2+ to form tin oxides and hydrates. Also, it prevents oxidation of the final products.

Synthesis of TiN Nanoparticles by Explosion of Ti Wire in Nitrogen Gas

Nano-sized Titanium nitride powders were synthesized by electrical explosion of Ti wire under nitrogen atmosphere ranging from 0.2 to 1.5 atm. Electron microscopy and X-ray diffraction studies revealed that the reaction products are cube-shaped single phase TiN nanoparticles. The lattice parameter of TiN nanoparticles increased with nitrogen pressure in the chamber. The nitrogen content of nanoparticles was estimated from their lattice parameter being comparable to the stoichiometric composition of TiN. Small amount of TiN0:3 phase was formed when nitrogen pressure in the chamber was low. [doi:10.2320/matertrans.M2009297]

Thermal stability of nitride coatings formed by ion–plasma deposition

Titanium nitride and chromium nitride coatings were formed on a gray cast iron by condensation from a plasma phase in vacuum with the ion bombardment of the sample surface by titanium or chromium plasma flows in a residual nitrogen atmosphere. The element and phase composition of coatings were studied before and after annealing for 1–43 h in air at temperature 700 °C using Auger electron spectroscopy (AES) and X-ray diffraction (XRD). It is established that titanium nitride coatings are single-phase TiN system with a (1 1 1) preferred growth orientation, and chromium nitride coatings—a two-phase system: CrN and Cr 2N phases. The annealing of coatings at the atmospheric pressure and the temperature of 700 °C in the range of 1–43 h results in the deceleration of the oxidation process of the material substrate for chromium nitride with respect to titanium nitride coatings.

Fast Shape Evolution of TiN Microcrystals in Combustion Synthesis

Single-phase TiN crystalline powder consisting of microcrystals has been prepared by combustion synthesis. During the drastic combustion reaction with a high reaction temperature and rapid heating rate, TiN microcrystals undergo a fast shape evolution process and finally develop into various crystallization shapes, such as quasi-spherical grains, faceted cubes or pyramids, and dendrites. The formation mechanisms of different crystal shapes are discussed in light of basic crystal growth theories. It is proposed that, at the initial stage, quasi-spherical TiN crystals are formed first by diffusion-controlled continuous growth; by a faceting process, flat surfaces then appear in several low-index directions on the quasi-spherical crystals, and at last, well-faceted crystals are produced by two-dimensional nucleation and layered growth. In addition, interesting TiN dendrites are observed, probably arising from the fast cooling rate in combustion synthesis. The dendrites grow quickly in three orthogonal directions, with each growth unit exhibiting a 4-fold symmetry and sometimes a half-octahedral pyramid head.

Superhard nanocomposite coatings of TiN/Si 3N 4 prepared by reactive direct current unbalanced magnetron sputtering

Approximately 1.5-μm-thick superhard nanocomposite coatings of TiN/Si 3N 4 with varying silicon contents were deposited on silicon and stainless steel (SS 304) substrates by reactive direct current (DC) unbalanced magnetron sputtering. An asymmetric bipolar-pulsed DC power supply and a DC power supply were used to sputter Si and Ti targets, respectively in Ar + N 2 plasma. Structural characterization of the coatings was done using X-ray diffraction (XRD). The bonding structure of the nanocomposite coatings was characterized by X-ray photoelectron spectroscopy (XPS). The elemental composition of the TiN/Si 3N 4 nanocomposite coatings was determined using energy dispersive X-ray analysis. The mechanical properties of the coatings were measured using a nanoindentation hardness tester. The surface morphology of the coatings was studied using atomic force microscopy. The nanocomposite coatings exhibited a broad (200) reflection of cubic TiN phase in the XRD data. There was a significant broadening of the (200) reflection with an increase in the silicon content in the nanocomposite coatings, which suggested a decrease in the average crystallite size. Nanoindentation data showed that about 1.5-μm-thick TiN/Si 3N 4 nanocomposite coatings exhibited a maximum hardness of 5200 kg/mm 2 and an elastic modulus of 340 GPa at a silicon concentration of approximately 12 at.%. The hardness and the elastic modulus of the nanocomposite coatings decreased with further increase in the silicon content. Structural changes as a result of heating (400–850 °C) of the nanocomposite coatings in air were characterized using micro-Raman spectroscopy. The Raman data showed that the nanocomposite coatings started to oxidize at 800 °C as compared to TiN, which have been oxidized even at 500 °C. To isolate the oxidation-induced spectral changes as a result of heating of the coatings in air, the samples were also annealed in vacuum at 850 °C under similar conditions. The Raman data of the vacuum-annealed coatings showed no phase transformation even after annealing up to 850 °C. The corrosion behaviors of single-phase TiN and TiN/Si 3N 4 nanocomposite coatings deposited on stainless steel substrates were investigated using potentiodynamic polarization in 3.5% NaCl solution. The results indicated that the nanocomposite coatings exhibited superior corrosion resistance as compared to the uncoated substrate. The wear data showed that the nanocomposite coatings also exhibited better wear resistance as compared to the uncoated substrate.