排序方式: 共有24条查询结果,搜索用时 15 毫秒
11.
Defect engineering in semiconducting oxides: Control of ZnO surface potential via temperature and oxygen pressure
下载免费PDF全文
![点击此处可从《American Institute of Chemical Engineers》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The technological usefulness of a semiconductor often depends on the types, concentrations, charges, spatial distributions, and mobilities of the atomic‐scale defects it contains. For semiconducting metal oxides, defect engineering is relatively new and involves complex transport and reaction networks. Surface‐based methods hold special promise in nanostructures where surface‐to‐volume ratios are high. This work uses photoreflectance augmented by X‐ray photoelectron spectroscopy to show that the surface potential VS for Zn‐terminated ZnO(0001) can be manipulated over a significant range 54.97–79.08 kJ/mol (0.57–0.82 eV) via temperature and the partial pressure of O2. A defect transport model implies this variation in VS should affect the injection rate of oxygen interstitials by a factor of three. Such injection plays an important role in controlling the concentrations of oxygen vacancies deep in the bulk, which often prove troublesome as trapping centers in photocatalysis and photovoltaics and as parasitic emitters in light‐emitting devices. © 2015 American Institute of Chemical Engineers AIChE J, 62: 500–507, 2016 相似文献
12.
Charlotte T. M. Kwok Richard D. Braatz Silke Paul Wilfried Lerch Edmund G. Seebauer 《American Institute of Chemical Engineers》2010,56(2):515-521
Technologies such as solid‐phase epitaxial regrowth and millisecond annealing techniques have led to a wide range of maximum temperatures and heating rates for activating dopants and eliminating ion implantation damage for transistor junction formation. Developing suitable annealing strategies depends on mathematical models that incorporate accurate defect physics. The present work describes a model that includes a newly discovered representation of defect annihilation at surfaces and of near‐surface band bending, together with an improved representation of interstitial clustering. Key parameters are determined by maximum likelihood (ML) estimation and maximum a posteriori (MAP) estimation. The model yields a substantially improved ability to model the behavior of implanted boron over a wide range of annealing conditions. © 2009 American Institute of Chemical Engineers AIChE J, 2010 相似文献
13.
Andrew S. Dalton Yevgeniy V. Kondratenko Edmund G. Seebauer 《Chemical engineering science》2010,65(6):2172-2176
Molecular dynamics simulations reveal a new picture for diffusion dynamics on the surface of amorphous silicon. The primary transport mechanism differs substantially from that observed on crystalline surfaces, in which small numbers of highly mobile adatoms or vacancies form and subsequently diffuse over substantial distances. Instead, diffusion takes place via large numbers of single atoms or dimers that move roughly one atomic diameter and are associated with highly strained rings having four atoms. 相似文献
14.
Richard D. Braatz Richard C. Alkire Edmund G. Seebauer Timothy O. Drews Effendi Rusli Mohan Karulkar Feng Xue Yan Qin Michael Y.L. Jung Rudiyanto Gunawan 《Computers & Chemical Engineering》2006,30(10-12):1643
This paper describes applications of molecular simulation to microelectronics processes and the subsequent development of techniques for multiscale simulation and multiscale systems engineering. The progression of the applications of simulation in the semiconductor industry from macroscopic to molecular to multiscale is reviewed. Multiscale systems are presented as an approach that incorporates molecular and multiscale simulation to design processes that control events at the molecular scale while simultaneously optimizing all length scales from the molecular to the macroscopic. It is discussed how design and control problems in microelectronics and nanotechnology, including the targeted design of processes and products at the molecular scale, can be addressed using the multiscale systems tools. This provides a framework for addressing the “grand challenge” of nanotechnology: how to move nanoscale science and technology from art to an engineering discipline. 相似文献
15.
This work examines two partial oxidation reactions over oxides (alcohols dehydrogenation to aldehydes and aldehydes esterification
to esters) to determine how reaction rates can be quantitatively correlated with physical properties of the bulk catalysts.
We show that while electronegativity difference, Δχ, metal–oxygen bond strength, E
M-O fail utterly, oxygen partial charge, qO, and oxygen Madelung potential, VMad (O), do provide limited correlations for the set of roughly twelve oxides examined. However, oxygen electronic polarisability,
αO, does a much better job. We rationalise this finding in terms of the concept of chemical hardness in what appears to be the
first successful application of this idea to oxide reactivity.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
16.
This study focuses on the optimal control of rapid thermal annealing (RTA) used in the formation of ultrashallow junctions needed in next-generation microelectronic devices. Comparison of different parameterizations of the optimal trajectories shows that linear profiles give the best combination of minimizing junction depth and sheet resistance. Worst-case robustness analysis of the optimal control trajectory motivates improvements in feedback control implementations for these processes. This is the first time that the effects of model uncertainties and control implementation inaccuracies are rigorously quantified for RTA. 相似文献
17.
O G?dje M Peyerl T Seebauer P Lamm H Mair B Reichart 《Canadian Metallurgical Quarterly》1998,13(5):533-9; discussion 539-40
OBJECTIVE: Monitoring of cardiac preload is mainly performed by measurement of central venous and pulmonary capillary wedge pressure in combination with assessment of cardiac output, applying the pulmonary arterial thermal dilution technique. However, the filling pressures are negatively influenced by mechanical ventilation and the pulmonary artery catheter is criticized because of its inherent risks. Measurement of right atria, right ventricular, global end diastolic and intrathoracic blood volume index by arterial thermal dye dilution utilizing the COLD-system may represent an alternative. METHODS: In 30 CABG patients with an uncomplicated postoperative course the mentioned parameters were measured 1, 3, 6, 12 and 24 h postoperatively to prove their qualification as preload indicators: As patients received no inotropic support, changes of cardiac index and stroke volume index must correlate to changes of presumably preload indicating parameters. RESULTS: When arterial and pulmonary arterial thermal dilution were compared, no differences were found; the correlation coefficient being 0.96, the bias 0.16 l/min per m2 (2.4%) and coefficients of variation did not exceed 7%. Changes of central venous pressure, capillary wedge pressure, right atrial end diastolic volume index and right ventricular end diastolic volume index did not correlate at all to changes of cardiac and stroke volume index (coefficients ranged from -0.01 to 0.28). In contrast, intrathoracic and global end diastolic blood volume indices with coefficients from 0.76 to 0.87, did show a good correlation to cardiac and stroke volume index. CONCLUSION: Central venous pressure, capillary wedge pressure, right atrial and right ventricular end diastolic volumes are no suitable preload parameters in cardiac surgery intensive care, compared to intrathoracic and global end diastolic blood volumes. The latter show a higher clinical value and can be obtained by less invasive methods, as no pulmonary artery catheter is required. 相似文献
18.
Vaidyanathan Subramanian Nicholas Ndiege E.G. Seebauer Mark A. Shannon Richard I. Masel 《Thin solid films》2008,516(15):4784-4792
Micron thick tantalum pentoxide (Ta2O5) films have been proposed as thermal insulating layers in microchemical systems, but so far it has been difficult to deposit thick enough films over complex substrates. So far sol–gel films cracked upon heating whenever the film thicknesses were above 350 nm. A 350 nm thick film is too thin for effective insulation. Other techniques are not suitable for coating the complex structures associated with microchemical systems. In this paper we report sol–gel synthesis of 1.6 μm thick tantalum pentoxide (Ta2O5) films. The films are almost crack free, and adhere to silicon surfaces even upon flashing to 900 °C. The key to the synthesis is the addition of Polyvinylpyrrolidine (PVP) to the sol. Films grown in the absence of PVP all show cracks upon calcination to 900 °C while few cracks are seen with PVP. X-ray diffraction and Fourier transform infra red analysis show that orthorhombic Ta2O5 is formed in all cases. X-ray photoelectron spectroscopy shows the O:Ta ratio to be 2.8:1. This shows that sol–gel is a viable process for making the micron thick films of Ta2O5 needed as insulators for microchemical systems. 相似文献
19.
Navaneetha Krishnan NandakumarEdmund G. Seebauer 《Thin solid films》2011,519(11):3663-3668
Spatially uniform, carbon-free thin films of V2O5 were deposited on silicon by chemical vapor deposition using vanadium oxide triisopropoxide and water as gaseous precursors, in the temperature range of 100-300 °C. Films with substantial crystallinity were obtained for deposition temperatures as low as 180 °C. The “neat” chemistry that nominally leaves no fragments of ligand or water in the solid promotes film purity and reduces the deposition temperature needed for crystallization. Such deposition temperatures also open up additional possibilities for using crystalline vanadia on fragile substrates such as polymers for electronics and optical applications. 相似文献
20.
Edmund G. Seebauer Meredith C. Kratzer 《Materials Science and Engineering: R: Reports》2006,55(3-6):57-149
Native point defects control many aspects of semiconductor behavior. Such defects can be electrically charged, both in the bulk and on the surface. This charging can affect numerous defect properties such as structure, thermal diffusion rates, trapping and recombination rates for electrons and holes, and luminescence quenching rates. Charging also introduces new phenomena such as nonthermally photostimulated diffusion, thereby offering distinctive mechanisms for defect engineering. The present work incorporates the first comprehensive account of semiconductor defect charging, identifying correspondences and contrasts between surfaces and the bulk as well as among semiconductor classes (group IV, groups III–V, and metal oxides). For example, small lattice parameters, close-packed unit cells, and basis atoms with large atomic radii all inhibit the formation of ionized interstitials and antisites. The charged defects that exist in III–V and oxide semiconductors can be predicted with surprising accuracy from the chemical potential and oxygen partial pressure of the ambient. The symmetry-lowering relaxations, formation energies, and diffusion mechanisms of bulk and surface defect structures often depend strongly on charge state with similar qualitative behavior, although for a given material surface defects do not typically take on the same configurations or range of stable charge states as their counterparts in the bulk. 相似文献