Effect of deposition temperature on key optoelectronic properties of electrodeposited cuprous oxide thin films

The cuprous oxide (Cu₂O) thin films were electrodeposited with different reaction temperatures. The structural, morphological, optical, photoluminescence and photo response properties of the deposited films were analyzed. XRD analysis reveals cubic crystal structure for the deposited films with polycrystalline nature. The film deposited at room temperature possess high crystallite size of 37 nm. The surface morphology shows that by increasing the deposition temperature pyramid shaped morphology changes. Laser Raman study confirms the peaks 109, 148, 219, 415 and 635 cm^?1 conforms the Cu₂O phase formation. The band gap of the films are 2.02, 2.10 and 2.27 eV for the RT, 40 and 50 °C, respectively. The photoluminescence spectral analysis contains an emission peak at 618 nm confirm the formation of Cu₂O. The photo response study confirms the ohmic nature of the films. The film electrodeposited at room temperature showed good I–V curve at the illumination of 300 W cm^?2.     

Ti-Si-N复合膜的界面相研究

为了揭示Ti_Si_N复合膜中Si₃N₄界面相的存在方式及其对薄膜力学 性能的影响 ，采用x射线衍射仪、高分辨透射电子显微镜、俄歇电子能谱仪和显微硬度仪对比研究了磁 控溅射Ti_Si_N复合膜和TiN/Si₃N₄多层膜的微结构和力学性能. 实 验结果表明 ，Ti_Si_N复合膜均形成了Si₃N₄界面相包裹TiN纳米晶粒的微结构. 其中低Si 含量的Ti_Si_N复合膜中Si₃N₄界面相的厚度小于1nm，且以晶体态 存在，薄膜 呈现高硬度. 而高Si含量的Ti_Si_N复合膜中的Si₃N₄界面相以非晶 态存在，薄 膜的硬度也相应降低. 显然，Ti_Si_N复合膜中Si₃N₄界面相以晶体 态形式存在 是薄膜获得高硬度的重要微结构特征，其强化机制可能与多层膜的超硬效应是相同的. 关键词： Ti－Si－N复合膜 界面相 微结构 超硬效应     

Improving the tribological performances of graphite-like carbon films on Si3N4 and SiC by using Si interlayers

Si interlayers were used to obtain the excellent tribological performances of graphite-like carbon (GLC) film on silicon nitride (Si₃N₄) and silicon carbide (SiC). The microstructure and mechanical characteristics of the as-prepared GLC films with Si interlayers were investigated by scanning electron microscopy, Raman spectroscopy, nanoindention and scratch test. The tribological behaviors of GLC-coated and uncoated Si₃N₄ and SiC were comparatively studied by a ball-on-disc tribo-meter in both dry and water environments. Results showed that the Si interlayers were dense and bonded well with both the substrates and GLC layers. The as-prepared GLC films exhibited excellent tribological performances in both dry and water environments. More importantly, the stably mild wear without any delamination was obtained in water by using Si interlayer. The mechanisms of friction reduction and anti-wear performances of GLC films on the two ceramics with Si interlayers under different environmental conditions were discussed, as well as the corresponding models were deduced.     

Influence of 120 MeV Si9+ ion irradiation on ZnTe semiconductor thin films

ABSTRACT

ZnTe (Zinc Telluride) is a potential semiconducting material for many optoelectronic devices like solar cells and back contact material for CdTe-based solar cells. In the present study, ZnTe thin films were prepared by thermal evaporation technique and then irradiated with 120?MeV Si⁹⁺ ions at different fluences. These films are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV–Visible spectroscopy techniques. XRD study confirms increased crystallinity and grain growth for post-irradiated ZnTe thin films for fluences, up to 1?×?10¹¹ ions cm^?2. However, the grain size and crystallinity decreased for higher fluence-exposed samples. SEM images confirm the observed structural properties. Modification of the surface morphology of the film due to the ion irradiation with different fluences is studied. Optical band gap of film is decreased from 2.31?eV (pristine) to 2.17?eV after irradiation of Si⁹⁺ ions.     

Characterization of SiON/InP MOS structure with sulfidation, fluorination, and hydrogenation

Liquid phase deposited SiON film on InP with (NH₄)₂S treatment shows superior electrical characteristics due to the reduction of native oxides and sulfur passivation. Simultaneously, HF in SiON liquid phase deposition solution can effectively reduce residual native oxides on InP and provide fluorine passivation in SiON/InP film and interface. With post-metallization annealing (PMA), hydrogen ions can further passivate defects in SiON/InP film and interface. With these treatments, the PMA-LPD-SiON/(NH₄)₂S-treated InP MOS structure shows excellent electrical characteristics. With the physical thickness of 5.4 nm, the leakage current densities can be as low as 1.25×10^?7 and 6.24×10^?7 A/cm² at ±2 V, and the interface state density is 3.25×10¹¹ cm^?2?eV^?1.     

Tribological Behavior of Multiply-Alkylated Cyclopentanes (MACs)-Cu Nanoparticles Composite Thin Film

Multiply-alkylated cyclopentanes (MACs) composite thin films containing Cu nanoparticles are fabricated on the octadecyltrichlorosilane (OTS)-modified substrate by a spin-coating technique. The thickness, wetting behavior, and nanoscale morphologies of the films are characterized by means of ellipsometry, contact angle measurement, and atomic force microscope (AFM). The friction and wear behaviors of the thin films sliding against Si₃N₄ ball are examined on a UMT-2MT tribometer in a ball-on-disk contact mode. The worn surfaces of the OTS-MAC-Cu composite film and the counterpart Si₃N₄ balls are investigated with a scanning electron microscope. Water contact angle on OTS-MAC-Cu composite film is higher than that of OTS-MAC film. OTS-MAC-Cu composite film exhibits higher load-carrying capacity and better friction reduction and antiwear behavior as compared with OTS-MAC film. This may be attributed to the load-carrying and self-repairing property of the Cu nanoparticles in the composite film and the formation of a transfer layer composed of OTS, MAC, and Cu on the rubbing surface of the counterpart ball.     

Quantitative analysis of hydrogen in amorphous silicon using Raman scattering spectroscopy

Hydrogenated amorphous silicon (a‐Si:H) films were studied using infrared and Raman spectroscopy. We have experimentally found that ratios of Raman scattering cross‐sections for Si–H to Si–Si bonds and for Si–H₂ to Si–Si bonds are equal to 0.65 ± 0.07 and 0.25 ± 0.03, respectively. It allows to measure the concentration of hydrogen in a‐Si:H films. The developed approach can be applied for in situ control of hydrogen in a‐Si:H films and also suitable for thin a‐Si:H films on substrates that are opaque in infrared spectral region. Copyright © 2013 John Wiley & Sons, Ltd.     

Effect of deposition time on structural and physical properties of Cu<Subscript>2</Subscript>CdSnS<Subscript>4</Subscript> thin films prepared by spray pyrolysis technique: experimental and ab initio study

Cu₂CdSnS₄ (CCdTS) thin films were synthesized using chemical spray pyrolysis deposition technique. The effect of various deposition times (20, 40, 60 min) on growth of these films was investigated. The as-synthesized Cu₂CdSnS₄ thin films were characterized by X-ray diffraction (XRD), ultraviolet–visible (UV–Vis) spectroscopy, Raman spectroscopy and Hall Effect measurements. The XRD pattern of Cu₂CdSnS₄ structured in stannite phase with preferential orientations along (112) planes. Raman spectrum revealed very strong peak at about 333 cm^?1. The films have the direct optical band gaps of 1.39–1.5 eV. The optimum hole mobility was found to be 3.212 × 10¹ cm² v^?1 s^?1 for the film deposited on 60 min. The electronic structure and optical properties of the stannite structure Cu₂CdSnS₄ were obtained by ab initio calculations using the Korringa–Kohn–Rostoker method combined with the Coherent Potential Approximation (CPA), as well as CPA confirms our results.     

Blue photoluminescence from SiGeSiO2 co-sputtered films

A blue photoluminescence band centered at 440 nm was observed from SiGeSiO₂ co-sputtered films at room temperature. This band gains intensity after the film was annealed at a temperature around 900°C in N₂ atmosphere. From analysis of photoluminescence excitation, Raman and X-ray photoelectron spectra, it turns out that the luminescence is probably from some interfacial state between Si_1−xGe_x nanoparticles and the SiO₂ matrix.     

Structural Characterization of RF‐Sputtered a‐C:N Thin Films by Raman,IR, and X‐ray Reflectometry Spectroscopies

Abstract

Amorphous carbon nitride thin films (a‐C:N) were deposited from a carbon target, at room temperature onto silicon substrates, by reactive RF sputtering in a gas mixture of argon and nitrogen. The structural properties of these films have been studied by Raman, infrared (IR), and X‐ray reflectometry spectroscopies. Both the IR and Raman spectra of the a‐C:N films reveal the presence of C–C, C?C, C?N, and C≡N bonding types. The Raman spectra analysis shows, an increase of the C≡N triple bonds content when the concentration of nitrogen C(N₂) in the gas mixture is increased. The Raman intensities ratio between the disorder (D) and graphitic (G) bands increases with C(N₂) suggesting an increased disorder with the incorporation of nitrogen in the carbon matrix. The effect of C(N₂) on the density of a‐C:N films was also investigated by X‐ray reflectometry measurement. The increase of the nitrogen concentration C(N₂) was found to have a significant effect on the density of the films: as C(N₂) increases from 0 to 100%, the density of the a‐C:N films decreases slightly from 1.81 to 1.62 g/cm³. The low values of density of the a‐C:N films were related (i) to the absence of C–N single bonds, (ii) to the increase of disorder introduced by the incorporation of nitrogen in the carbon matrix, and (iii) to the presence of the bands around 2350 cm^?1 and 3400 cm^?1 associated with the C–O bond stretching modes and the O–H vibration, respectively, suggesting a high atmospheric contamination by oxygen and water. The presence of these bands suggests the porous character of the studied samples.     

Chemical control of physical properties in silicon nitride films

Amorphous hydrogenated silicon nitride (a-SiN _x H _y ) films were prepared by plasma-enhanced chemical vapor deposition (PECVD). The physical properties and chemical structures of the resulting materials were systematically investigated. Results reveal that the a-SiN _x H _y films similarly consist of four kinds of Si–N groups, including Si₃N₄, H–Si–N₃, H₂–Si–N₂, and Si₃–Si–N. Deposition at 13.56 MHz and 300 ^°C with flow ratio of SiH₄/NH₃=30/30 sccm leads to the yield of Si_0.39N_0.38H_0.23 films that exhibit excellent properties of high uniformity, high elastic modulus, moderate refractive index and optical band gap, low UV absorption, and ultralow residual stress (?0.17 MPa). Such Si_0.39N_0.38H_0.23 films hold considerable promise for applications in solar cells and infrared sensors. In contrast, an increase of Si or N content in a-SiN _x H _y films will cause the degradation of the properties, so that the films are unsuitable for solar cells. Moreover, a new conception of network degree was proposed to evaluate and explain the properties of a-SiN _x H _y films. Particularly, this work discloses the relationships between the chemical structures and physical properties, and suggests a basic approach to the yield of a-SiN _x H _y films with controlled physical properties.     

Influence of silicon on the microstructure and mechanical properties of Zr-Si-N composite films

A series of Zr-Si-N composite films with different Si contents were synthesized in an Ar and N₂ mixture atmosphere by the bi-target reactive magnetron sputtering method. These films’ composition, microstructure and mechanical properties were characterized by energy dispersive spectroscopy, X-ray diffraction, scanning electron microscopy, atomic force microscopy and nanoindentation. Experimental results revealed that after the addition of silicon, Si₃N₄ interfacial phase formed on the surface of ZrN grains and prevented them from growing up. Zr-Si-N composite films were strengthened at low Si content with the hardness and elastic modulus reaching their maximum values of 29.8 and 352 GPa at 6.2 at% Si, respectively. With a further increase of Si content, the crystalline Zr-Si-N films gradually transformed into amorphous, accompanied with a remarkable fall of films’ mechanical properties. This limited enhancement of mechanical properties in the Zr-Si-N films may be due to the low wettability of Si₃N₄ on the surface of ZrN grains.     

Synthesis of Ge-Sn at high pressure and high temperature in a laser-heated diamond anvil cell

Ge–Sn compound is predicted to be a direct band gap semiconductor with a tunable band gap. However, the bulk synthesis of this material by conventional methods at ambient pressure is unsuccessful due to the poor solubility of Sn in Ge. We report the successful synthesis of Ge–Sn in a laser-heated diamond anvil cell (LHDAC) at ~7.6 GPa &; ~2000 K. In situ Raman spectroscopy of the sample showed, apart from the characteristic Raman modes of Ge TO (Г) and β-Sn TO (Г), two additional Raman modes at ~225 cm^?1 (named Ge–Sn₁) and ~133 cm^?1 (named Ge–Sn₂). When the sample was quenched, the Ge–Sn₁ mode remained stable at ~215 cm^?1, whereas the Ge–Sn₂ mode had diminished in intensity. Comparing the Ge–Sn Raman mode at ~225 cm^?1 with the one observed in thin film studies, we interpret that the observed phonon mode may be formed due to Sn-rich Ge–Sn system. The additional Raman mode seen at ~133 cm^?1 suggested the formation of low symmetry phase under high P–T conditions. The results are compared with Ge–Si binary system.     

Plasma-assisted hot filament chemical vapor deposition of AlN thin films on ZnO buffer layer: toward highly c-axis-oriented,uniform, insulative films

c-Axis-oriented aluminum nitride (AlN) thin film with improved quality was deposited on Si(111) substrate using ZnO buffer layer by plasma-assisted hot filament chemical vapor deposition. The optical and electrical properties and surface morphology as well as elemental composition of the AlN films deposited with and without ZnO buffer layer were investigated using a host of measurement techniques: X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, field emission scanning electron microscopy (FESEM), and current–voltage (I–V) characteristic measurement. The XRD and XPS results reveal that the AlN/ZnO/Si films are free of metallic Al particles. Also, cross-sectional FESEM observations suggest formation of a well-aligned, uniform, continuous, and highly (002) oriented structure for a bi-layered AlN film when Si(111) is covered with ZnO buffer. Moreover, a decrease in full width at half maximum of the E₂ (high)-mode peak in Raman spectrum indicates a better crystallinity for the AlN films formed on ZnO/Si substrate. Finally, I–V curves obtained indicate that the electrical behavior of the AlN thin films switches from conductive to insulative when film is grown on a ZnO-buffered Si substrate.     

Evaluation of Si3N4/Si interface by UV Raman spectroscopy

The stresses at Si₃N₄/Si (1 0 0), (1 1 1) and (1 1 0) interfaces were measured by UV Raman spectroscopy with a 364 nm excitation laser whose penetration depth into the Si substrate was estimated to be 5 nm. The Si₃N₄ films were formed on Si (1 0 0), (1 1 1) and (1 1 0) using nitrogen-hydrogen (NH) radicals produced in microwave-excited high-density Xe/NH₃ mixture plasma. The localized stress detected from Raman peak shift was compressive at the (1 0 0) interface, and tensile at the (1 1 1) and (1 1 0) interfaces. The results showed that stress had strong correlation with the total density of subnitrides at the Si₃N₄/Si interface, and also with the full-width at half-maximum (FWHM) of Si the 2p_3/2 photoemission spectrum arising from the substrate. We believe that the localized stress affected subnitride formation because the amount of subnitride and the FWHM of Si 2p_3/2 decreased while the interface stress shifted in the tensile direction.     

Growth mechanism of tantalum silicides by interdiffusion

Interdiffusion studies were conducted to understand the atomic mechanism of the diffusing species and the growth mechanism of the phases. Integrated diffusion coefficients and the ratio of tracer diffusion coefficients were estimated for these analyses. The activation energies for the integrated diffusion coefficients were calculated as 550?±?70 and 410?±?39?kJ/mol in the TaSi₂ and Ta₅Si₃ phases, respectively. In the TaSi₂ phase, Ta has a slightly lower but comparable diffusion rate with respect to Si, although no Ta–Ta bonds are present in the crystal. In the Ta₅Si₃ phase, Si has a higher diffusion rate, which is rather unusual, if we consider the atoms in the nearest-neighbour positions for both the elements. The ratio of Si to Ta tracer diffusion coefficients is found to be lower in the Si-rich phase, TaSi₂, compared to the Si-lean phase, Ta₅Si₃, which is also unusual. This indicates the type of structural defects present. An analysis on the growth mechanism of the phases indicates that duplex morphology and the Kirkendall marker plane should only be present in the TaSi₂ phase. This is not present in the Ta₅Si₃ phase due to the very high growth rate of the TaSi₂ phase, which consumes most of the Ta₅Si₃ phase layer. The problems in the calculation method used previously by others in this system are also explained.     

A New Silicon-Containing Arylacetylene Resin With Amine Groups as Precursor to Si−C−N Ceramic

A new preceramic precursor was prepared by chlorination and ammoniation reaction of poly(methylsilyleneethynylenephenyleneethynylene) (MSEPE), [?SiH(CH₃)? C≡C?C₆H₄?C≡C?]_n. The obtained amine-modified silicon-containing arylacetylene resin (MSEPE-An) was a liquid polymer at room temperature and could be thermally cross-linked at temperatures lower than 200°C. The chemical structure of MSEPE-An was characterized by FTIR, ¹H NMR, and GPC. The pyrolysis of the cured MSEPE-An was carried out in N₂ atmosphere up to 1450°C to produce a Si?C?N ceramic composite. The ceramic composite was analyzed by FTIR and X-ray diffraction techniques. The electromagnetic wave absorption properties of a paraffin sample with 10 vol% Si?C?N ceramic powders were characterized in a frequency range of 2–18 GHz, according to a conventional reflection/transmission technique. Experimental results demonstrated that the Si?C?N ceramic composite provided good electromagnetic wave absorption performance.     

Effect of irradiating ion fluence on optical properties of ZnO1−x:Nx thin films

Swift heavy ion (SHI) irradiation is an effective technique to modify the optical properties of the materials. In the present investigation, the effect of 100?MeV?Ag⁷⁺ SHI irradiation fluence on the optical properties of ZnO_1?x:N_x thin films was studied. The post irradiation spectroscopic characterizations such as UV–VIS reflectance spectroscopy, Raman spectroscopy and photoluminescence (PL) spectroscopy analysis were carried out. The studies imply that when the SHI passes through the solid, the higher electronic stopping power of ions can weaken oxygen bonds in ZnO, resulting in the formation of donor defects such as oxygen vacancies and zinc interstitials. The formation of donor defects has been acknowledged through the increase in bandgap with irradiating ion fluence. The blue shift observed from the Raman spectra for the 3?×?10¹³ ions/cm² fluence-irradiated films implies the existence of compressive stress in the films. The PL analysis acknowledges the formation of donor defects upon irradiation. Furthermore, it conveys that the presence of N atoms in ZnO lattice leads to the formation of a less number of defects as compared with undoped ZnO while irradiation.     

Thin-film formation of Si clathrates on Si wafers

In this study, we prepared Si clathrate films (Na₈Si₄₆ and Na_xSi₁₃₆) using a single-crystalline Si substrate. Highly oriented film growth of Zintl-phase sodium silicide, which is a precursor of Si clathrate, was achieved by exposing Na vapour to Si substrates under an Ar atmosphere. Subsequent heat treatment of the NaSi film at 400 °C (3 h) under vacuum (<10⁻² Pa) resulted in a film of Si clathrates having a thickness of several micrometres. Furthermore, this technique enabled the selective growth of Na₈Si₄₆ and Na_xSi₁₃₆ using the appropriate crystalline orientation of Si substrates.     

Chemical,optical, and electrical characterization of Ga2O3 thin films grown by plasma-enhanced atomic layer deposition

Thin Ga₂O₃ films were grown on Si (100) using trimethylgallium (TMG) and oxygen as the precursors through plasma-enhanced atomic layer deposition. The depositions were made over a temperature range of 80–250?°C with a growth per cycle of around 0.07 nm/cycle. Surface self-saturating growth was obtained with TMG pulse time ≥20?ms?at a temperature of 150?°C. The root mean square surface roughness of the obtained Ga₂O₃ films increased from 0.1?nm to 0.3?nm with increasing the growth temperature. Moreover, the x-ray photoelectron spectroscopy analysis indicated that the obtained film was Ga-rich with the chemical oxidation states Ga³⁺ and Ga¹⁺, and no carbon contamination was detected in the films after Ar⁺ sputtering. The electron density of films measured by x-ray reflectivity varied with the growth temperature, increasing from 4.72 to 5.80?g/cm³. The transmittance of Ga₂O₃ film deposited on a quartz substrate was obtained through ultraviolet visible (UV–Vis) spectroscopy. An obvious absorption in the deep UV region was demonstrated with a wide band gap of 4.6–4.8?eV. The spectroscopic ellipsometry analysis indicated that the average refractive index of the Ga₂O₃ film was 1.91?at 632.8?nm and increased with the growth temperature due to the dense structure of the films. Finally, the I-V and C-V characteristics proved that the Ga₂O₃ films prepared in this work had a low leakage current of 7.2?×?10^?11 A/cm² at 1.0?MV/cm and a high permittivity of 11.9, suitable to be gate dielectric.