Signature analysis and defect detection in layered manufacturing of ceramic sensors and actuators

This paper presents the concept of a process signature for the use of online signature analysis and defect detection in the layered manufacturing (LM) of ceramic sensors and actuators. To achieve the high quality of parts built by the fused deposition of ceramics (FDC), an online process-monitoring system is implemented to detect the processing defects. Using a process signature extracted from the image of a layer captured by the monitoring system, an ideal image is created that is then compared to the original image to detect and identify the defects. Some results of signature analysis and defect detection for single-material and multi-material parts are also presented.Received: 22 July 1999, Accepted: 21 October 2001, Published online: 29 October 2003 Correspondence to: Mohsen A. JafariThis work was supported by the Office of Naval Research under grant # N-0014-96-1-1175. Ref. US Patent # S-5738817, April 14, 1998.     

Heavy arsenic doping of silicon grown by atmospheric pressure selective epitaxial chemical vapor deposition

Selective epitaxial Si with a high arsenic concentration of 2.2×10¹⁹ atoms/cm³ was deposited at a high growth rate of 3.3 nm/min under atmospheric pressure. It was confirmed that this method had excellent selectivity and produced films having good crystalline quality, abrupt dopant profiles at the interfaces, and smooth surfaces. The growth mechanism is discussed in terms of the relationship between the effects of arsenic surface segregation and etching by hydrogen chloride.     

溶液温度对电化学沉积氧化亚铜薄膜相成分和显微结构的影响

用电化学方法在不锈钢基体上沉积多晶Ｃｕ２Ｏ薄膜并用Ｘ射线衍射和扫描电进行了分析研究了溶液温度对薄膜相组成、晶粒尺寸和择优取向的影响，当溶液的ＰＨ＝９，温度低于５０℃时得到的是Ｃｕ２Ｏ／Ｃｕ复相薄膜，纯Ｃｕ２Ｏ薄膜可在溶液温度高于５０℃时获得，纯Ｃｕ２Ｏ薄膜具有（１００）择优取向，实验发现薄膜的晶粒尺寸随溶液温度的增加从０．１２μｍ增加到０．６５μｍ。     

喷雾沉积快速凝固技术的发展与展望

喷雾沉积是制取大体积快凝材料的一种新工艺。本文综述了它的产生和发展，概述了其基本原理和过程控制。对该领域今后的发展动向，提出了一些新看法。     

Electrical and optical properties of oxygen doped GaN grown by MOCVD using N2O

Oxygen doped GaN has been grown by metalorganic chemical vapor deposition using N₂O as oxygen dopant source. The layers were deposited on 2″ sapphire substrates from trimethylgallium and especially dried ammonia using nitrogen (N₂) as carrier gas. Prior to the growth of the films, an AIN nucleation layer with a thickness of about 300? was grown using trimethylaluminum. The films were deposited at 1085°C at a growth rate of 1.0 μm/h and showed a specular, mirrorlike surface. Not intentionally doped layers have high resistivity (>20 kW/square). The gas phase concentration of the N₂O was varied between 25 and 400 ppm with respect to the total gas volume. The doped layers were n-type with carrier concentrations in the range of 4×10¹⁶ cm⁻³ to 4×10¹⁸ cm⁻³ as measured by Hall effect. The observed carrier concentration increased with increasing N₂O concentration. Low temperature photoluminescence experiments performed on the doped layers revealed besides free A and B exciton emission an exciton bound to a shallow donor. With increasing N₂O concentration in the gas phase, the intensity of the donor bound exciton increased relative to that of the free excitons. These observations indicate that oxygen behaves as a shallow donor in GaN. This interpretation is supported by covalent radius and electronegativity arguments.     

Drying of Prone to Twist Boards in a Pre-Twisted Position

A method to minimize twist has been investigated; i.e., drying the boards in a pre-twisted position. It has been found that Norway spruce boards can be deformed toward straightness by this method. The force exerted by a board on its holders during drying in a pre-twisted position has been measured. When the variation in torsional stiffness as a function of temperature and moisture content is accounted for, it is found that a creep deformation of the board occurs both during the drying phase and the cooling phase. In addition to mechano-sorptive creep, a deformation released by a change in temperature also seems to occur.     

冷弯型钢纵向变形的理论分析及计算

对冷弯型钢的纵向变形过程进行了力学分析，得到了变形微分方程，求得了转动角的理论公式，并对其变形形状进行了分析计算。     

Effect of chloride ions on immersion plating of copper onto porous silicon from a methanol solution

The effect of chloride ions (Cl⁻) during the immersion plating of copper onto porous silicon (PS) from a methanol (MeOH) solution has been studied. The presence of Cl⁻ in the Cu²⁺ solution was found to slow down the rate of copper deposition, as confirmed by inductively coupled argon plasma emission spectroscopy and X-ray photoelectron spectroscopy measurements. The threshold concentration of Cl⁻ at which the deposition of copper is very severely diminished was found to be 0.1 M. The inhibition effect is discussed on the basis of the rest potential values of PS and polarization curve measurements. They revealed that the rest potential of PS upon dipping in these solutions appears to direct the metal deposition. Current density-potential curves show that at Cl⁻ concentrations higher than 0.1 M, the reduction of Cu ions proceeds in two steps; the reduction of Cu(II) to Cu(I) followed by the reduction of Cu(I) to Cu(0). This suggests that Cu(I) species in MeOH solution can be stable over a certain potential range and this stability of Cu(I) is responsible for the inhibition of metal deposition. Fourier transform infrared spectroscopy and scanning electron microscopy (SEM) were also performed to investigate the structural changes and characterizations of PS samples after the plating process.     

Film morphology and reaction rate for the CVD of tungsten by the WF6—SiH4 reaction

Journal of Electronic Materials - Low pressure chemical vapor deposition (LPCVD) of tungsten (W) by SiH4 reduction of WF6 on Si(100) surfaces was studied in a single-wafer, cold-wall reactor over a...