Low-temperature Deposition Process Research Articles

Langmuir probe and optical emission spectroscopy studies in magnetron sputtering plasmas for Al-doped ZnO film deposition

This work reports investigation of the Al-doped ZnO (AZO) film deposition process, at different working pressures, in a conventional magnetron sputtering system. The primary goal of this study is to investigate the plasma formation and deposition process using various diagnostic tools, by utilizing low-temperature deposition process. In addition, this paper also presents a systematic Langmuir probe (LP) analysis procedure to determine the maximum information about plasma parameters. For the present study, we have extensively used LP method to characterize the deposition process for the control of plasma parameters. Along with the LP method, we have also used optical emission spectroscopy diagnostic to examine the favorable deposition condition for the fabrication of conductive AZO film. Utilizing diagnostics, this also reports measurements of ion current density, substrate temperature, and deposition rates to fabricate low resistivity films of ∼3 mΩ cm.

Tribotechnical and Mechanical Properties of Coarse-Grained and Submicrocrystalline Ti–Al–V (VT6) Alloy with a Ti–C–Mo–S Multi-Component Antifriction Coating

The results of a comparative study of the effect of a nanophase Ti–C–Mo–S coating on tribotechnical and mechanical properties of a VT6 (α+β)-titanium alloy in its coarse-grained and submicrocrystalline states are presented. To form the coating of a Ti–C–Mo–S chemical composition, use is made of a low-temperature magnetron-plasma deposition process at the substrate temperature not higher than 300°С. With a 1–1.3μm multi-component nanophase coating, the friction coefficient in a friction pair of the like grain structure (submicrocrystalline or coarse-grained) is shown to reduce by a few factors, while the wear resistance appears to increase by two orders of magnitude. The high strength achieved in the alloy due to the formation of the submicrocrystalline structure is maintained.

Optical absorption spectroscopy of facing targets and conventional magnetron sputtering during process of Al-doped ZnO films

Facing targets sputtering (FTS) is a promising process for low-temperature TCO film deposition and for the significant reduction of damage in film structure by suppression of the direct impinging of high-energy particles due to confining plasma between two facing magnetic fields compared with conventional magnetron sputtering (CMS). In this study, FTS was compared with CMS by measuring Zn densities during the deposition process of Al-doped ZnO films with DC and 13.56MHz RF discharge at various process conditions. Optical absorption spectroscopy (OAS) was adopted for measuring Zn densities, for which a hollow cathode lamp was used as a source light of a 213.9nm line, which was selected to measure absorption coefficients and to calculate the ground state densities of Zn atoms. When RF power was applied, Zn densities were lower than in DC conditions in both CMS and FTS. Interestingly, in FTS, Zn densities were observed to be lower than in CMS regardless of the RF and DC powers, indicating an increase of plasma density associated with the high ionization rate and collision rate of FTS.

Fabrication and characterization of metal/insulator/semiconductor structures based on TiO2 and TiO2/SiO2 thin films prepared by low-temperature arc vapor deposition

The present work involves the fabrication and characterization of two different metal/insulator/semiconductor (MIS) structures: Pd/TiO2/Si and Pd/TiO2/SiO2/Si. The TiO2 thin films on the n-type Si 〈100〉 substrate were deposited using low-temperature arc vapor deposition process. The electrical characterizations of MIS structures were investigated using capacitance-voltage and current density-voltage measurements. The effects of annealing on the properties of the films were also studied. Furthermore, the structural, surface morphological, and electrical properties of the devices were compared with those obtained using other deposition techniques.

Low temperature amorphous silicon carbide thin film formation process on aluminum surface using monomethylsilane gas and trichlorosilane gas

The low-temperature chemical vapor deposition process of silicon carbide (SiC) on an aluminum surface was developed. In order to prepare the reactive substrate surface, a silicon interlayer containing silicon dimers at its surface was formed using trichlorosilane gas at 600°C. Next, the SiC thin film was formed at room temperature using monomethylsilane gas. Silicon, carbon and silicon-carbon bond in the obtained film were detected by various evaluations. The SiC film was amorphous and about 5-nm thick.

低温原子层沉积氧化铝作为有机电致发光器件的封装薄膜

In order to avoid the damage of high reaction temperature to OLEDs,the low-temperature atomic layer deposition( ALD) process was introduced to deposite Al2O3 film for the encapsulation of OLEDs. However,the low temperature condition would decrease the uniformity of the film. In order to suppress the generating of vacancy,the pumping gas time( PGT) was increased during each cycle to discharge the products adequately. The micrographs,calcium test and lifetime test of OLEDs show that the film deposited at low temperature is almost the same with that deposited at high temperature,and the temperature effect to OLEDs is not negligible. The water vapor transmission rate( WVTR) of the film can reach to 8. 6 × 10- 4g /( m2·d),so the lifetime of the device with the encapsulation layer can be increased effectively.

Low-temperature preparation of AgIn5S8/TiO2 heterojunction nanocomposite with efficient visible-light-driven hydrogen production

AgIn5S8 and AgIn5S8/TiO2 heterojunction nanocomposite with efficient photoactivity for H2 production were prepared by a low-temperature water bath deposition process. The resultant AgIn5S8 shows an absorption edge at ∼720 nm, corresponding to a bandgap of ∼1.72 eV, and its visible-light-driven photoactivity (100.1 μmol h−1) for H2 evolution is 9 times higher than that (11 μmol h−1) of the product derived from a hydrothermal process, while the obtained AgIn5S8/TiO2 heterojunction nanocomposites prepared by using commercially available TiO2 nanoparticles (P25) as TiO2 source exhibit remarkably improved photoactivity as compared to the pristine AgIn5S8, and the AgIn5S8/TiO2 nanocomposite with molar ratio of 1:10 shows a maximum photocatalytic H2 evolution rate (371.1 μmol h−1), which is 4.3 times higher than that (85 μmol h−1) of the corresponding AgIn5S8/TiO2 nanocomposite derived from a hydrothermal method. This significant enhancement in the photocatativity of the present AgIn5S8/TiO2 nanocomposite can be ascribed to the better dispersion of the AgIn5S8 formed on TiO2 nanoparticle surfaces and the more intimate AgIn5S8/TiO2 heterojunction structure during the water bath deposition process under continuously stirring as compared to the corresponding nanocomposite derived from a hydrothermal method. This configuration of nanocomposite results in fast diffusion of the photogenerated carriers in AgIn5S8 towards TiO2, which is beneficial for separating spatially the photogenerated carriers and improving the photoactivity. The present findings shed light on the tuning strategy of spectral responsive region and photoactivity of photocatalysts for efficient light-to-energy conversion.

Effect of sodium on material and device quality in low temperature deposited Cu(In,Ga)Se2

Abstract Sodium is known to play an important role for the performance optimization of Cu(In,Ga)Se 2 (CIGSe) thin film solar cells, i.e. it is found to significantly increase the open-circuit voltage ( V OC ). For this work CIGSe absorbers were produced in a low temperature deposition process on polyimide substrates with varying sodium content. In agreement with previous studies we find an increase of V OC and overall solar cell performance with increasing sodium content and a decrease of the overall performance for very high sodium content. At the same time time-resolved photoluminescence measurements indicate that the minority carrier lifetime decreases from 50 ns to about 5 ns for increasing sodium content in the absorber. This correlation was found to be valid for three different types of low-temperature CIGSe deposition processes. The results can be explained by an increase in deep defect density with increasing Na content, proportional to the increased net charge carrier density as measured by capacitance–voltage profiling. For very high sodium content this leads to an actual decrease in the overall performance of the solar cells.

Low temperature and rapid deposition of ZnO nanorods on Si(100) substrate with tunable optical emissions

This research article describes the large scale fabrication of ZnO nanorods of various shapes on Si(100) substrate, by using metalorganic precursor of Zn in solutions with microwave as the source of energy. This is a low temperature, environmental friendly and rapid thin film deposition process, where ZnO nanorods (1–3 μm length) were grown only in 1–5 min of microwave irradiation. All as-synthesized nanorods are of single crystalline grown along the <0001> crystallographic direction. The coated nanorods were found to be highly dense having a thickness of ∼1–3 μm over the entire area 20 mm × 20 mm of the substrate. The ZnO thin film comprising of nanorods exhibits good adhesion with the substrate. A possible mechanism for the initial nucleation and growth of ZnO is discussed. A cross over from a strong visible light emission to an enhanced UV emission is observed, when the nature of the surfactants are varied from polymeric to ionic and nonionic. The position of the chromaticity coordinates in yellow region of the color space gives an impression of white light generation from these coatings by exciting with a blue laser.

Raman spectroscopy of nanocrystalline Mn-doped BiFeO3 thin films

Enhancement of magnetic and electric properties in multiferroic Mn-substituted BiFeO3 thin films (BiFe1− x Mn x O3 with x = 0.00–0.05) grown via the low-temperature chemical solution deposition process on low-cost substrates like indium tin oxide (ITO)/glass and silicon is reported in this work. A detailed structural analysis by high-resolution X-ray diffraction and Raman spectroscopy indicates that the grown films exhibit rhombohedral distorted perovskite structure without any impure phase. Raman spectroscopic analysis shows all 13 Raman active (4A1 + 9E) phonon modes corresponding to distorted rhombohedral BFO R3c structure. BFO thin film with 5% Mn substitution showed maximum saturation and remnant magnetisation (M s = 16.70 emu/g and M r = 2.58 emu/g) and remarkably reduced leakage current due to distortion in the spin cycloid structure and suppression of oxygen vacancies due to partial replacement of Fe3+ ion by Mn3+ ion, respectively. These enhanced multifunctional properties highlight the potential applications of BFMO system in thin film devices which can couple magnetic and ferroelectric order parameters.

High-performance bilayer flexible resistive random access memory based on low-temperature thermal atomic layer deposition.

We demonstrated a flexible resistive random access memory device through a low-temperature atomic layer deposition process. The device is composed of an HfO2/Al2O3-based functional stack on an indium tin oxide-coated polyethylene terephthalate substrate. After the initial reset operation, the device exhibits a typical bipolar, reliable, and reproducible resistive switching behavior. After a 104-s retention time, the memory window of the device is still in accordance with excellent thermal stability, and a 10-year usage is still possible with the resistance ratio larger than 10 at room temperature and at 85°C. In addition, the operation speed of the device was estimated to be 500 ns for the reset operation and 800 ns for the set operation, which is fast enough for the usage of the memories in flexible circuits. Considering the excellent performance of the device fabricated by low-temperature atomic layer deposition, the process may promote the potential applications of oxide-based resistive random access memory in flexible integrated circuits.

Low temperature processing of redispersed tin doped indium oxide nanoparticle coatings

The deposition of transparent conducting oxide (TCO) coatings using for example chemical vapor deposition, spray pyrolysis or a conventional sol–gel routine usually needs high temperatures and is therefore only applicable to temperature-stable substrates like glass. The deposition of TCO coatings on temperature-sensitive substrates requires low-temperature deposition processes like redispersed nanoparticle suspensions combined with e.g. the dip-coating technique. To obtain a tin doped indium oxide (ITO) nanoparticle suspension for the coating process, ITO nanopowder is redispersed in a mixture of solvents, cross-linking agents and stabilizers. In this work it is shown that four different stabilizers and mixtures of these stabilizers can be used and how the choice of the stabilizers influences the properties of the coatings concerning the reflectance of the surface, the layer composition, that means the porosity and the surface roughness of the layers, and the electrical conductivity.

Final capping passivation layers for long-life microsensors in real fluids

Final capping insulation layer is a critical step in the microfabrication process that determines the lifetime of analytical microsensors in real fluids. Actual processes encounter considerable limitations as (i) organic passivation layers do not provide a satisfying long-term protection against liquids and (ii) inorganic passivation processes (dielectric materials deposition and patterning) are very aggressive for the underlying layers, imposing severe constraints on the integration of sensitive materials. We present here a low temperature deposition process of high quality silicon nitride Si3N4 using ICP-CVD technique combined with a lift-off based process to pattern conformal deposition, in order to avoid harsh treatments such as wet or dry etching. High-density SiNx films with low H content (5×1020at/cm3) were synthesized at 100°C with controlled uniformity (5%), refractive index (2.025 at 830nm), etch rate in buffered hydrofluoric acid (8nm/min), residual stress (−500MPa), breakdown field (3.9MV/cm) and dielectric constant (6.0). In order to validate the compatibility of this passivation process with long-term fluids analysis, microelectrodes were fabricated and their lifetime in natural seawater was evaluated. Their active surfaces were defined by patterning the insulation layer. Special care was given to their accurate estimation through the modelling of chronoamperometric curves. Reproducible and stable electrochemical response was obtained for months (>50 days), demonstrating a considerably extended lifetime in harsh liquid media.

The kinetics of low-temperature spatial atomic layer deposition of aluminum oxide

Spatial atomic layer deposition can be used as a high-throughput manufacturing technique in functional thin film deposition for applications such as flexible electronics. This, however, requires low-temperature deposition processes. We have investigated the kinetics of low-temperature (<100°C) spatial atomic layer deposition of alumina from tri-methyl aluminum and water. The water partial pressure and the exposure time were identified as the critical parameters in this process.

High Quality SiO2 Obtained From Diluted SOG for Low Temperature TFT Fabrication Process

Currently, the flexible electronics research field is of high interest because of the development of low cost products, such as solar cells and LCDs. Low temperature deposition processes are required in order to use flexible substrates. Nevertheless, the performance of the electronic devices built at temperatures below 350°C is not as good as in CMOS technology. Thus, physical and electrical properties of semiconductor and insulator materials deposited at these low temperatures must be improved. In this work, characterization of SiO2 annealed at 200°C obtained from diluted Spin On Glass (SOG) is presented. The optical and electrical characterization showed that the refractive index (n) and dielectric constant (k) values are similar to those of thermally grown SiO2. TFTs based on a-SiGe:H were fabricated to demonstrate the quality of the dielectric here obtained

Low-Thermal-Budget Solution Processing of Thin Films of Zinc Ferrite and Other Complex Oxides

ABSTRACTFurther miniaturization of magnetic and electronic devices demands thin films of advanced nanomaterials with unique properties. Spinel ferrites have been studied extensively owing to their interesting magnetic and electrical properties coupled with stability against oxidation. Being an important ferrospinel, zinc ferrite has wide applications in the biological (MRI) and electronics (RF-CMOS) arenas. The performance of an oxide like ZnFe2O4depends on stoichiometry (defect structure), and technological applications require thin films of high density, low porosity and controlled microstructure, which depend on the preparation process. While there are many methods for the synthesis of polycrystalline ZnFe2O4powder, few methods exist for the deposition of its thin films, where prolonged processing at elevated temperature is not required. We report a novel, microwave-assisted, low temperature (&lt;100°C) deposition process that is conducted in the liquid medium, developed for obtaining high quality, polycrystalline ZnFe2O4thin films on technologically important substrates like Si(100). An environment-friendly solvent (ethanol) and non-hazardous oxide precursors (β-diketonates of Zn and Fe in 1:2 molar ratio), forming a solution together, is subjected to irradiation in a domestic microwave oven (2.45 GHz) for a few minutes, leading to reactions which result in the deposition of ZnFe2O4films on Si (100) substrates suspended in the solution. Selected surfactants added to the reactant solution in optimum concentration can be used to control film microstructure. The nominal temperature of the irradiated solution, i.e., film deposition temperature, seldom exceeds 100°C, thus sharply lowering the thermal budget. Surface roughness and uniformity of large area depositions (50x50 mm2) are controlled by tweaking the concentration of the mother solution. Thickness of the films thus grown on Si (100) within 5 min of microwave irradiation can be as high as several microns. The present process, not requiring a vacuum system, carries a very low thermal budget and, together with a proper choice of solvents, is compatible with CMOS integration. This novel solution-based process for depositing highly resistive, adherent, smooth ferrimagnetic films on Si (100) is promising to RF engineers for the fabrication of passive circuit components. It is readily extended to a wide variety of functional oxide films.

Nanochannel-Directed Growth of Multi-Segment Nanowire Heterojunctions of Metallic Au1–xGex and Semiconducting Ge

We report on the synthesis of multi-segment nanowire (NW) junctions of Au(1-x)Ge(x) and Ge inside the nanochannels of porous anodic aluminum oxide template. The one-dimensional heterostructures are grown with a low-temperature chemical vapor deposition process, assisted by electrodeposited Au nanowires (AuNWs). The Au-catalyzed vapor-liquid-solid growth process occurs simultaneously in multiple locations along the nanochannel, which leads to multi-segment Au(1-x)Ge(x)/Ge heterojunctions. The structures of the as-grown hybrid NWs, analyzed by using transmission electron microscopy and energy-dispersive X-ray spectroscopy elemental mapping, show clear compositional modulation with variable modulation period and controllable junction numbers. Remarkably, both GeNW and Au(1-x)Ge(x)NW segments are single crystalline with abrupt interfaces and good crystallographic coherences. The electronic and transport properties of individual NW junctions are measured by using a multi-probe scanning tunneling microscope, which confirms the semiconducting nature of Ge segments and the metallic behavior of Au(1-x)Ge(x) segments, respectively. The high yield of multiple segment NW junctions of a metal-semiconductor can facilitate the applications in nanoelectronics and optoelectronics that harness multiple functionalities of heterointerfaces.

On the Mechanisms of SiO2 Thin-Film Growth by the Full Atomic Layer Deposition Process Using Bis(t-butylamino)silane on the Hydroxylated SiO2(001) Surface

With the continuing miniaturization of electronic devices, the atomic layer deposition (ALD) technique has become the preferred choice for the deposition of dense, conformal thin films. Efficient precursors that enable low-temperature deposition processes are of critical importance to ensure high-quality thin films with low impurity levels. Herein, we present a first-principles study on a full cycle of an ALD process using bis(t-butylamino)silane (BTBAS) as the precursor for developing a SiO2 thin film on the hydroxylated SiO2(001) surface with ozone as the oxidizing agent. Two possible deposition pathways were systematically studied. One leads to crystalline growth of the film, and the other gives rise to disordered growth layers. Detailed elementary processes on the surface of the substrate and the associated energetics were examined. We show that the crystalline growth pathway is thermodynamically more favorable, but the disordered growth pathway is kinetically more facile. Given enough time to settle,...

Comparative Study of Different Back-Contact Designs for High-Efficiency CIGS Solar Cells on Stainless Steel Foils

In this paper, Cu(In,Ga)Se <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> (CIGS) solar cells on stainless steel foils were developed using a three-stage evaporation processes at low and high substrate temperatures. Different CIGS back-contact designs were used: a thin Ti adhesion layer together with a Mo single layer, Mo bilayer, and Mo bilayer in combination with either an Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> or TiN impurity diffusion barrier layer. Solar cells on contacts with an Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> and a TiN barrier coating showed no improvement in performance compared with the cells on Ti/Mo/Mo triple-layer contact, regardless of the CIGS deposition temperature. The variation of the Mo back-contact designs with no impurity diffusion barrier showed a significant decrease in solar cell performance when thin Mo contacts were used. Furthermore, capacitance to voltage measurements showed a decrease in the carrier concentration in CIGS grown on thin Mo contacts compared with the layers for solar cells on Ti/Mo/Mo triple layer structures. Best cell efficiencies of 17.3% were obtained using a Mo back-contact with a thin Ti adhesion layer, in combination with a low-temperature CIGS deposition process with no additional oxide or nitride impurity diffusion barrier layer on stainless steel foils.

나노물질의 선택적 레이저소결을 이용한 유연전기소자 구현 연구현황

대부분의 유연전기소자는 플라스틱, 옷감, 종이와 같이 고온에 민감한 물질이기 때문에 열에 민감한 기판 위에 금속을 증착하고 패터닝할 수 있는 저온 공정의 개발이 필요하다. 최근 기존의 광식각과 진공증착 방법을 이용하지 않고 액상으로 금속 나노입자의 박막을 형성하고 선택적 레이저 소결을 이용하여 플라스틱에 열적손상을 최소화하고 고해상도의 금속 패터닝을 방법이 많은 연구가 활발히 진행되고 있다. 본 논문에서는 본 연구실에서 활발히 수행중인 나노물질의 선택적 레이저소결법을 이용하여 유연 디스플레이와 유연태양전지와 같은 유연전기소자의 개발 동향에 대해 알아보고 앞으로의 발전방향에 대해 논의한다.