Papers by Keyword: Low Temperature Deposition

Abstract: Based on the selenium ion beam assisted magnetron sequential sputtering technology, low temperature deposition of CIS thin-film solar cells in high quality can be achieved. By comparing with the method of conventional gas phase atomic deposition, and through simulated analysis from the perspective of diffusion uniformity, numerical calculation on the depth of ion beam injection is proceeded. First, according to the classical collision theory in molecular dynamics, the theoretical calculation on the process of ion implantation is done; the concentration distribution of implanted selenium ions can be got by using TRIM program for simulation analysis. On this basis, the concentration distribution of selenium ion after diffusion can be further obtained. Finally, the calculation model is established; through comparison and analysis, when the selenium diffusion uniformity is same in the both conditions, the substrate temperature T₁ needed for ion beam assisted deposition and the substrate temperature T₂ needed for gas phase atomic deposition are respectively calculated. The calculation results show that on the premise of merely considering the depth of implanted ions, from the perspective of the diffusion uniformity, the selenium ion beam assisted deposition technique can obviously reduce the substrate temperature comparing with traditional vapor deposition technology.

Abstract: Synthetic diamond has remarkable properties comparable with natural diamond and hence is a very promising material for many various applications (sensors, heat sink, optical mirrors, cold cathode, tissue engineering, etc.). Nowadays, deposition of diamond films is normally employed in chemical vapor deposition (CVD) usually at high temperatures (800900 °C), what limit its application to high melting substrates. Gravimetric (mass) sensors belong to the major categories of chemical sensors and the most common type of mass sensor is the bulk acoustic quartz crystal microbalance (QCM). This contribution deals with a nanocrystalline diamond (NCD) growth from the H₂/CH₄/CO₂ gas mixture at low temperature (400 °C) by pulsed linear antenna microwave plasma system on 10 MHz circular AT-cut quartz resonators substrate. Gas sensor based on the NCD-coated QCM was developed for detection of ammonia (NH₃) at room temperature. Measurements not only confirmed the functionality of this first published NCD-coated QCM sensor, but in addition its sensitivity was twofold to a virgin QCM sensor with a gold active layer.

Abstract: A DC dual magnetron sputtering system with graphite (C) and silicon (Si) targets was used to grow stoichiometric and non-stoichiometric silicon carbide (SixCy) thin films at low temperature. Two independently DC power sources were used to enable the total discharge power be shared, under certain proportions, between the Si and C magnetron cathodes. The motivation was to control the sputtering rate of each target so as to vary the stoichiometric ratio x/y of the deposited films. The species content, thickness and chemical bonds of as-deposited SixCy films were studied by Rutherford backscattering spectroscopy (RBS), profilometry analysis and Fourier transform infrared absorption (FTIR), respectively. Overall, the present work reveals a new reliable plasma sputtering technique for low temperature growth of amorphous SixCy thin films with the capability of tuning the degree of formation of a-SiC, a-Si and a-C bonds in the film bulk.

Abstract: This research proposes a novel low temperature manufacturing method to make a wireless accelerometer on a flexible substrate. The substrate deposition temperature is 100°C without causing any strain and stress problem. Since the thermal conductivity of the traditional Si is 1.48 W/ (cm-K), which is 25 times of the flexible substrate, i.e. 0.06-0.0017 W/ (cm-K), thus the power leakage through the substrate can be saved by the new design. The key technology is to integrate a thermal bubble accelerometer and a wireless RFID antenna on the same substrate, such that the accelerometer is very convenient for fabrication and usage. In this paper the heaters and the thermal piles are directly adhering on the substrate surface without the traditional floating structure. Thus the structure is much simpler and cheaper for manufacturing, and much more reliable in large acceleration impact condition without broken. Furthermore, the molecular weight of xenon gas (131.29 g/mol) is much larger than carbon dioxide (44.01 g/mol), thus the performance of the accelerometer will be increased. In addition, the shape of the chamber is changed as a semi-cylindrical one instead of the conventional rectangular type. The average sensitivity is increased by 15%. In addition, if one applies only xenon gas but keeping the rectangular chamber, then the response speed can be increased by 23%. Moreover, if one applies both Xe and the semi-cylindrical chamber, then the response speed can be increased by 43%.

Abstract: The low temperature deposition principle of magnetron sputtering was discussed. Reactive magnetron sputtering technique was used to gain titanium nitride (TiN) thin films on W18Cr4V high-speed steel substrates at low temperature. A series of experiments had been conducted to study the properties of TiN films. The experimental results showed that at the low temperature(<140 °C), magnetic sputtering can be used for the deposition of TiN film with compact, uniform and high nano-hardness, and their tribological properties were excellent, which co-determined by the film structure of low temperature magnetron sputtering and the counter-parts of rubbing pairs.

Abstract: A completely interconnected macroporous and microporous poly(l-lactic acid) (PLLA) scaffold was fabricated from a PLLA–dioxane–water ternary system by an advanced manufacturing technology called low-temperature deposition manufacturing. A proper fraction of water and PEG added into the polymer solution induces liquid-liquid phase separation and gelation. The liquid-liquid phase separation brings in a new micro morphology and gelation effect produces higher fabrication accuracy.

Abstract: We have examined the effect of oxidant in metalorganic chemical vapor deposition (MOCVD) of Al2O3 gate insulator on MOSFET electrical properties. High channel mobility of 311 cm2/Vs for Al2O3/SiC MOSFET is demonstrated when the Al2O3 gate insulator is deposited on HF-treated substrate at 190oC using triethyl-aluminum (TEA) and O2 as Al source and oxidant gas, respectively. This is much higher than that of Al2O3/SiC MOSFET when Al2O3 gate insulator was deposited with TEA and H2O at the same temperature. In addition, channel mobility at high gate electric field can be improved by using O2 as oxidant gas and effective mobility of 207 cm2/Vs is obtained at SiO2 equivalent gate electric field of 1.5 MV/cm.

Abstract: 4H-SiC MOSFETs with Al2O3/SiC and Al2O3/SiOx/SiC gate structures have been fabricated and characterized. Al2O3 was deposited by metal-organic chemical vapor deposition (MOCVD) and the SiOx layer was formed by dry-O2 oxidation. Insertion of 1.2 nm-thickness-SiOx layer drastically improves the channel mobility of Al2O3/SiC-MOSFET and anomalously high field effect mobility (μFE) of 284 cm2/Vs was obtained. The μFE of Al2O3/SiOx/SiC-MOSFET with various SiOx thickness was investigated, and it was found that insertion of a thin SiOx layer (< 2 nm) followed by the low temperature deposition of Al2O3 results in Al2O3/SiOx/SiC-MOSFET with such a high channel mobility.

Abstract: ZnO nanorods grown by chemical bath methods are of great interest in photovoltaic and electronic device applications because they offer low cost, low temperature deposition techniques compared to conventional molecular beam vapor deposition and sputtering methods. Our previous studies of ZnO nanorods grown by chemical bath technique on indium tin oxide (ITO) coated glass substrates at 90 C for 8-10 hours resulted in uniform growth of hexagonally shaped closed nanorod structures. We used scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques to map changes in surface morphology of nanorods grown on various substrates. Morphology of ZnO nanorods at temperatures 80C, 90C, 95C and 100C for 9 hours of hydrothermal growth also resulted in hexagonal shaped nanorods of various sizes and surface roughness. In addition, we studied the changes in surface morphology of ZnO nanorods on indium tin oxide coated glass, aluminum coated glass, and conducting tin oxide glass substrate. In this paper, we present quantitative data on changes in cluster size and shape of nanorods as the growth substrate and deposition temperature are varied. We will also discuss conductivity changes of ZnO nanorods deposited on various substrates.

Abstract: We have fabricated and characterized MOS capacitors and lateral MOSFETs using Al2O3 as a gate insulator. Al2O3 films were deposited by metal-organic chemical vapor deposition (MOCVD) at temperatures as low as 190 oC using tri-ethyl-aluminum and H2O as precursors. We first demonstrate from the capacitance – voltage (C-V) measurements that the Al2O3/SiC interface has lower interface state density than the thermally-grown SiO2/SiC interface. No significant difference was observed between X-ray photoelectron spectroscopy (XPS) Si 2p spectrum from the Al2O3/SiC interface and that from the SiC substrate, which means the SiC substrate was not oxidized during the Al2O3 deposition. Next, we show that the fabricated lateral SiC-MOSFETs with Al2O3 gate insulator have good drain current – drain voltage (ID-VD) and drain current – gate voltage (ID-VG) characteristics with normally-off behavior. The obtained peak values of field-effect mobility (μFE) are between 68 and 88 cm2/Vs.