Growth and characterisation of SiC films deposited on a-SiO2/Si (100) substrates

Abstract

The growth of polycrystalline SiC films has been carried out by low pressure chemical vapour deposition in a horizontal quartz reaction chamber using tetramethylsilane and H2 as the precursor gas mixture. Silicon (100) wafers were used as substrates. A thin Si O₂ amorphous layer of ~6 nm was formed before SiC deposition to reduce the strain induced by the 8% difference in thermal expansion coefficients between SiC and Si. Samples were. analysed by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and infrared reflectivity. The structure of films grown at temperatures between 950 and 1150°C varies from amorphous to polycrystalline SiC. Preferential [111] orientation and columnar growth of polycrystalline films develops with increasing temperature.

MST/3317     

Effects of post-deposition annealing temperature and ambient on RF magnetron sputtered Sm<Subscript>2</Subscript>O<Subscript>3</Subscript> gate on n-type silicon substrate

Samarium oxide (Sm₂O₃) thin films with thicknesses in the range of 15–30 nm are deposited on n-type silicon (100) substrate via radio frequency magnetron sputtering. Effects of post-deposition annealing ambient [argon and forming gas (FG) (90% N₂ + 10% H₂)] and temperatures (500, 600, 700, and 800 °C) on the structural and electrical properties of deposited films are investigated and reported. X-ray diffraction revealed that all of the annealed samples possessed polycrystalline structure with C-type cubic phase. Atomic force microscope results indicated root-mean-square surface roughness of the oxide film being annealed in argon ambient are lower than that of FG annealed samples, but they are comparable at the annealing temperature of 700 °C (Argon—0.378 nm, FG—0.395 nm). High frequency capacitance–voltage measurements are carried out to determine effective oxide charge, dielectric constant and semiconductor-oxide interface trap density of the annealed oxide films. Sm₂O₃ thin films annealed in FG have smaller amount of effective oxide charge and semiconductor-oxide interface trap density than those oxide films annealed in argon. Current–voltage measurements are conducted to obtain barrier heights of the annealed oxide films during Fowler–Nordheim tunneling.     

Effect of growth temperature on structural, electrical and optical properties of dual ion beam sputtered ZnO thin films

ZnO epitaxial thin films were grown on p-type Si(100) substrates by dual ion beam sputtering deposition system. The crystalline quality, surface morphology, optical and electrical properties of as-deposited ZnO thin films at different growth temperatures were studied. Substrate temperature was varied from 100 to 600 °C at constant oxygen percentage O₂/(O₂ + Ar) % of 66.67 % in a mixed gas of Ar and O₂ with constant chamber pressure of 2.75 × 10^?4 mBar. X-Ray diffraction analyses revealed that all the films had (002) preferred orientation. The minimum value of stress was reported to be ?0.32 × 10¹⁰ dyne/cm² from ZnO film grown at 200 °C. Photoluminescence measurements demonstrated sharp near-band-edge emission (NBE) was observed at ~375 nm along with deep level emission (DLE) in the visible spectral range at room temperature. The DLE Peak was found to have decrement as ZnO growth temperature was increased from 200 to 600 °C. The minimum FWHM of the NBE peak of 16.76 nm was achieved at 600 °C growth temperature. X-Ray photoelectron spectroscopy study revealed presence of oxygen interstitials and vacancies point defects in ZnO film grown at 400 °C. The ZnO thin film was found to be highly resistive when grown at 100 °C. The ZnO films were found to be n-type conducting with decreasing resistivity on increasing substrate temperature from 200 to 500 °C and again increased for film grown at 600 °C. Based on these studies a correlation between native point defects, optical and electrical properties has been established.     

Solution-sol-gel processing of superconductors

Bulk materials and thin films of pure and homogeneous YBa₂Cu₃O_7−x and Bi₂Sr₂CaCu₂O_8+x compounds were prepared by a nanocomposite solution-sol-gel (SSG) method. The superconducting oxides of YBa₂Cu₃O_7−x and Bi₂Sr₂CaCu₂O_8+x were prepared at very low temperatures i.e. 750°C and 850°C, respectively by SSG method. Pellets sintered from these nanophasic sol powders showed sharp resistivity drops atT _c ∼ 90°K for YBa₂Cu₃O_7−x andT _c∼67°K for Bi₂Sr₂CaCu₂O_8+x . Thin films were prepared using triphasic sol of Y, Ba, Cu and tetraphasic sol of Bi, Sr, Ca and Cu on MgO and SrTiO₃ substrates. The triphasic sol coated on SrTiO₃ substrates and calcined at 800°C for 12h showed the formation of superconducting phase, YBa₂Cu₃O_7−x with preferred orientation along theC-axis. X-ray diffraction patterns of the Bi₂Sr₂CaCu₂O_8+x films on MgO substrate showed the formation of the superconducting phase with preferential orientation along the C-axis and the microwave absorption data as a function of temperature of this film revealed the onset temperature to be 90°K.     

Optical property and crystalline quarity of Si and Ge added β-Ga<Subscript>2</Subscript>O<Subscript>3</Subscript> thin films

A transparent electrode of β-Ga₂O₃ films for solar cells, flat panel displays and other devices, which consist in chemically abundant and ecological elements of gallium and oxygen, were grown on quartz or silicon substrates by RF magnetron sputtering using a sintered Ga₂O₃ target. The impurities of Si or Ge were also added into the grown films. The polycrystalline β-Ga₂O₃ grew by the thermal annealing after RF sputtering. Optical absorption measurements indicated that the grown β-Ga₂O₃ film after 600°C annealing have a band gap of about 5 eV.     

Growth of Bi1.5MgNb1.5O7 thin films on Pt/Ti/SiO2/Si substrates by RF magnetron sputtering

In this letter, bismuth magnesium niobate (Bi_1.5MgNb_1.5O₇, BMN) thin films were deposited on Pt/Ti/SiO₂/Si substrates by using radio-frequency magnetron sputtering at various substrate temperatures. Based on the phase compositions and microstructures of these samples, we discussed the nucleation and growth of the BMN thin films and how the substrate temperature influenced these processes. The thin film begins to crystallize at 450 °C, and the annealed films were all composed of the cubic pyrochlore phase with a strong (222)-preferred orientation. The film deposited at 450 °C exhibited a large dielectric constant of 173, and a tunability of 26.6 % was obtained at a max dc bias field of 0.8 MV/cm.     

A single phase semiconducting Ca-silicide film growth by sputtering conditions,annealing temperature and annealing time

Ca films were directly deposited on Si(100) substrates under the same sputtering power and Ar flux by Radio frequency (R.F.) magnetron sputtering system (MS) and were subsequently annealed at 800 °C for 90 min in a vacuum furnace. The structural and morphological features of the resultant films are tested by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive analysis of X-rays (EDAX). The cubic phase Ca₂Si film, the simple orthorhombic phase Ca₂Si film, and the tetragonal phase Ca₅Si₃ film are grown directly and individually on Si(100) substrates, respectively. The experimental results indicate that the selective growth of a single phase Ca-silicide from Ca–Si system of the existence of multiple silicide phases depends on sputtering conditions, annealing temperature, and annealing time. Besides, 800 °C is the adaptive annealing temperature for a single phase Ca-silicide film growth.     

Epitaxial growth and relaxation of γ-Al2O3 on silicon

0.5-10 nm-thick single crystal γ-Al₂O₃ films was epitaxially grown, at high temperature, on Si(001) and Si(111) substrates using electron-beam evaporation techniques. Reflection High Energy Electron Diffraction studies showed that the Al₂O₃ films grow pseudomorphically on Si (100) up to thickness of 2 nm. For higher thicknesses, a cubic to hexagonal surface phase transition occurs. Epitaxial growth and relaxation were also observed for Si(111). The film surfaces are smooth and the oxide-Si interfaces are atomically abrupt without interfacial layers.     

Optical and structural characteristics of Y<Subscript>2</Subscript>O<Subscript>3</Subscript> thin films synthesized from yttrium acetylacetonate

Yttrium oxide thin films are deposited on silicon substrates using the ultrasonic spray pyrolysis technique from the thermal decomposition of a β-diketonate, yttrium acetylacetonate (Y(acac)₃). The decomposition of Y(acac)₃ was studied by thermogravimetry, differential scanning calorimetry, mass spectrometry, and infrared spectroscopy. It was found that a β-diketone ligand is lost during the initial steps of decomposition of the Y(acac)₃. The rest of the complex is then dissociated or degraded partially until Y₂O₃ is obtained in the final step with the presence of carbon related residues. Then the Y(acac)₃ was used to synthesize Y₂O₃ thin films using the spray pyrolysis technique. The films were deposited on silicon substrates at temperatures in the range of 400–550 °C. The films were characterized by ellipsometry, infrared spectroscopy, atomic force microscopy, and X-ray diffraction. The films presented a low surface roughness with an index of refraction close to 1.8. The crystalline structure of the films depended on the substrate temperature; films deposited at 400 °C were mainly amorphous, but higher deposition temperatures (450–550 °C), resulted in polycrystalline with a cubic crystalline phase.     

Structural and electrical properties of RuO2 thin films prepared by rf-magnetron sputtering and annealing at different temperatures

Conductive ruthenium oxide (RuO₂) thin films have been deposited at different substrate temperatures on various substrates by radio-frequency (rf) magnetron sputtering and were later annealed at different temperatures. The thickness of the films ranges from 50 to 700 nm. Films deposited at higher temperatures show larger grain size (about 140 nm) with (200) preferred orientation. Films deposited at lower substrate temperature have smaller grains (about 55 nm) with (110) preferred orientation. The electrical resistivity decreases slightly with increasing film thickness but is more influenced by the deposition and annealing temperature. Maximum resistivity is 861 μΩ cm, observed for films deposited at room temperature on glass substrates. Minimum resistivity is 40 μΩ cm observed for a thin film (50 nm) deposited at 540°C on a quartz substrate. Micro-Raman investigations indicate that strain-free well-crystallized thin films are deposited on oxidized Si substrates.     

Structural and electrical properties of d.c. sputtered MnCo2O4 films

In the present work thin films of cobalt manganese oxides are investigated. The films were deposited by reactive ion plasma sputtering on sapphire and the cubic spinel MgO·2.5Al₂O₃ with the orientations (100) and (111). The electrical resistance of polycrystalline MnCo₂O₄ films was measured after annealing. Annealing in air at temperatures of 950–970°C leads to a decrease in the film resistivity. The characterization of the films was completed by structural investigations.     

The Development of Microstructure and Ferroelectric Properties of Bi<Subscript>4</Subscript>Ti<Subscript>3.96</Subscript>Nb<Subscript>0.04</Subscript>O<Subscript>12</Subscript> Thin Films

Bi₄Ti_3.96Nb_0.04O₁₂ thin films were successfully deposited on Pt(111)/Ti/SiO₂/Si(100) substrates by a sol–gel method and rapid thermal annealing. The effects of Nb-substitution and annealing temperature (500–800°C) on the microstructure and ferroelectric properties of bismuth titanate thin films were investigated. X-ray diffraction analysis reveals that the intensities of (117) peaks are relatively broad and weak at annealing temperatures smaller than 700°C. With the increase of annealing temperature from 500°C to 800°C, the grain size of Bi₄Ti_3.96Nb_0.04O₁₂ thin films increases. The Bi₄Ti_3.96Nb_0.04O₁₂ thin films annealed at 700°C exhibit the highest remanent polarization (2P _r), 36 μC/cm² and lowest coercive field (2E _c), 110 kV/cm. The improved ferroelectric properties can be attributed to the substitution of Nb⁵⁺ to Ti⁴⁺ in Bi₄Ti₃O₁₂ assisting the elimination of defects such as oxygen vacancy and vacancy complexes.     

The ferroelectric and optical properties of (Pb0.92La0.08)(Zr0.65Ti0.35)O3 thin films deposited by radio-frequency magnetron sputtering

Ferroelectric (Pb_0.92La_0.08)(Zr_0.65Ti_0.35)O₃ (PLZT) films have been prepared on Pt/Ti/SiO₂/Si and fused quartz substrates using radio-frequency (rf) magnetron sputtering at a deposition temperature of 650°C. X-ray diffraction analysis shows that the PLZT thin films on platinized silicon are polycrystalline with (100)-preferential orientation. A Al/PLZT/Pt capacitor has been fabricated and it shows that the films have excellent ferroelectric character, with saturation polarization (P _s), remanent polarization (P _r) and coercive field (E _c) of 32.8μC/cm², 24.3μC/cm² and 142 kV/cm, respectively. The PLZT thin films exhibit good insulating property and the leakage current density of the films on platinized silicon is only about 0.86 × 10⁻⁷ A/cm² at 200 kV/cm. By the optical transmission spectra measurements, the energy gap (E _g) of the PLZT films on fused quartz is found to be about 3.54 eV. The optical constants (n and k) of the films in the wavelength range of 250–900 nm are obtained by a Filmetrics F20 reflectance spectrometer.     

Growth and characterization of laser-deposited Ag-doped YBa2Cu3O7−x thin films on bare sapphire

Microstructural and superconducting properties of YBa₂Cu₃O_7−x thin films grownin situ on bare sapphire by pulsed laser deposition using YBa₂Cu₃O_7−x targets doped with 7 and 10 wt% Ag have been studied. Ag-doped films grown at 730°C on sapphire have shown very significant improvement over the undoped YBa₂Cu₃O_7−x films grown under identical condition. A zero resistance temperature of 90 K and a critical current density of 1·2×10⁶ A/cm² at 77 K have been achieved on bare sapphire for the first time. Improved connectivity among grains and reduced reaction rate between the substrate and the film caused due to Ag in the film are suggested to be responsible for this greatly improved transport properties.     

Anomalous phase formation during annealing of La2O3 thin films deposited by ion beam assisted electron beam evaporation

The fifty seven nm thick La₂O₃ thin films were deposited on Si (100) substrates. After deposition, the amorphones thin films, were amorphous, were annealed at 750 and 900 °C for 1 h. It was found that their amorphous structure had been crystallized to hexagonal and cubic structures, respectively. The phase formation of the La₂O₃ thin films was anomalous at higher annealing temperatures. The theory of heterogeneous nucleation was used to interpret the anomalous phase formation of La₂O₃ films. To investigate the effects of the phase structure on these properties, Refractive indexes and dielectric constants of different structures of La₂O₃ films were measured.     

Growth and characterization of yttrium oxide films by reactive magnetron sputtering

Yttrium oxide (Y₂O₃) is a promising ceramic material for electronic and optical applications due to its excellent properties. The purpose of this study is to characterize the effects of deposition parameters on the structure and composition of Y₂O₃ films. The films are grown on Si substrates by reactive magnetron sputtering at different substrate temperatures and oxygen pressures. The composition and structure of the films are studied by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. It is shown that the Y₂O₃ films deposited by reactive magnetron sputtering are mainly cubic phase and polycrystalline. The films are composed of Y-O, Y-O-Si, and Si-O bonds. Increasing substrate temperature induces the monoclinic to cubic phase transition and results in the formation of oxygen vacancies in the film. The preferred growth orientation of Y₂O₃ film is the (110) plane at low temperature, and it changes to the (111) plane at high temperature. The low temperature is preferable for the formation of Y-O bonds. The oxygen pressure influences on the concentration of Y-O bonds significantly. An optimal oxygen partial pressure for the formation of Y-O bonds exists during the film deposition. In addition, the deposited Y₂O₃ films exhibit excellent mechanical properties.     

Epitaxial growth of SrRuO3 thin films by RF sputtering and study of surface morphology

We report on the epitaxial growth of SrRuO₃ (SRO) thin films on Pt (111)/γ-Al₂O₃ (111) nSi (111) substrates. The grown thin films are crystalline and epitaxial as suggested by RHEED and XRD experiments. With the use of γ-Al₂O₃ (001)/nSi (001) and γ-Al₂O₃ (111)/nSi (111) substrates, crystalline but not epitaxial films have grown successfully. This result implies that lattice mismatch between nSi and SRO prevents the epitaxial growth of SRO film directly on nSi. However, the buffer Pt (111) layer mitigates lattice mismatch that provides to grow epitaxial film on nSi of quality. Morphological study shows a good surface with moderate roughness. Film grown at 700°C is smoother than the film grown at 750°C, but the variation of temperature does not affect significantly on the epitaxial nature of the films.     

Preparation and properties of Y2O3-doped ZrO2 thin films by the sol–gel process

Y₂O₃-doped ZrO₂ (YZ) thin films were prepared on alumina substrates by the dip-coating process. The dip-coating solution consisted of a homogeneous sol, and was prepared by using the respective chlorides as raw materials, with ethylene glycol, 2-butanol and distilled water as solvents. The thin films containing 0–20 mol % Y₂O₃ were successfully produced by thermal treatment above 600 °C. The characterization for the film preparation was performed by means of thermogravimetric–differential thermal analysis for the thermal analysis, and scanning electron microscopy for the morphological analysis and thickness measurements. The properties of the films were characterized in terms of a study of the crystalline phase, the crystallite size, the microstructure and the electrical conductivity by using X-ray diffraction, scanning electron microscopy and the complex impedance techniques. In all YZ thin films, the tetragonal phase was stable at low temperatures as a result of the crystallite size effect. However, at higher temperatures, the tetragonal phase was transformed into either the monoclinic phase or the cubic phase, depending on the doping concentration. The YZ thin film of 8 mol% Y₂O₃ content was stabilized to almost cubic phase at 1000 °C. Resonable conductivity behaviour at YZ was observed for the YZ thin films. The electrical conductivity of YZ thin films was similar to the values of the sintered body. This revised version was published online in November 2006 with corrections to the Cover Date.     

Crystallization process and electro-optical properties of In2O3 and ITO thin films

Amorphous indium oxide (In₂O₃) and 10-wt% SnO₂ doped In₂O₃ (ITO) thin films were prepared by pulsed-laser deposition. These films were crystallized upon heating in vacuum at an effective heating rate of 0.00847 °C/s, while the evolution of the structure was observed by in situ X-ray diffraction measurements. Fast crystallization of the films is observed in the temperature ranges 165–210 °C and 185–230 °C for the In₂O₃ and ITO films, respectively. The crystallization kinetics is described by a reaction equation, with activation energies of 2.31 ± 0.06 eV and 2.41 eV and order of reactions of 0.75 ± 0.07 and 0.75 for the In₂O₃ and ITO films, respectively. The structures of the films observed here during heating are compared with those obtained upon film growth at different temperatures. The resistivity of the films depends on the evolution of the structure, the oxygen content and the activation of tin dopants in the films. A low resistivity of 5.5 × 10⁻⁴ Ω cm was obtained for the In₂O₃ and ITO films at room temperature, after annealing to 250 °C the resistivity of the ITO film reduces to 1.2 × 10⁻⁴ Ω cm.     

The growth and transformation of Pd2Si on (111), (110) and (100) Si

Thin Pd films on (111), (110), (100) and amorphous Si substrates form [001] fiber textured Pd₂Si in the temperature range 100°–700°C. The degree of texture is a function of substrate orientation, increasing in the order amorphous Si, (100) Si, (110) Si and (111) Si. Only on the (111) Si substrate is the Pd₂Si film epitaxially oriented. Temperature-dependent growth on this orientation can be characterized by [001] textured growth, epitaxial azimuth orientation at the Si interface and progressive layer by layer formation of the mosaic crystal to the thin film surface.During Pd deposition, rapid non-diffusion-controlled growth of epitaxial Pd₂Si on (111) Si occurs at substrate temperatures of 100° and 200°C. An unidentified palladium silicide of low crystallographic symmetry forms during Pd deposition onto a 50°C substrate. The diffusion-controlled growth of Pd₂Si on (111) Si follows a t^0.5 dependence. The velocity constant is

$\text{k = 7 × 10}{}^{\mathrm{?2}}\text{exp}\text{?}\text{29200±800}\text{RT}\text{cm}{}^2\text{/}\text{sec}$

Palladium deposited on 100°C (111) Ge substrates reacts during deposition to form epitaxially oriented Pd₂Ge. However, growth of this phase at higher temperatures results in a randomly oriented film. The transformation of Pd₂Ge to PdGe is kinetically controlled. After a 15 min anneal at 560°±10°C in N₂ only PdGe is detectable on (111) Ge.The high temperature stability of thin film Pd₂Si is controlled by time- temperature kinetics. For a given annealing cycle, the nucleation and growth rates of the PdSi phase are inversely related to the crystalline perfection of Pd₂Si. Decreasing transformation rates follow the order (100), (110), (111) Si. formation of thin film Pd₂Si occurs by the formation of PdSi and subsequent growth of Si within the PdSi phase. After a 30 min N₂ anneal, initial transformation occurs at 735°C on (100) Si, 760°C on (110) Si and 840°C on (111) Si. Extended high temperature annealing produces a two-phase structure of highly twinned and misoriented Si and small PdSi grains that penetrate as much as 3 μm into the Si.