Low Temperature Silicon Film Deposition By Pulsed Cathodic Arc Process for Microsystem Technology  Researchers at Michigan Tech demonstrated for the first time the deposition of doped silicon films by pulsed cathodic vacuum arc techniques. The development of silicon thin films is attractive for many applications in the field of microelectronics and micromechanics such as thin film transistors, solar cells devices, and structural elements in microelectromechanical system (MEMS). The production of MEMS device quality silicon film materials at low temperature would further enable the integration of microsystems with microelectronics. To meet a growing variety of device technology requirements, attention is given to the processing methods to control the materials' growth and properties. As a technique for high quality film growth, cathodic vacuum arc deposition is characterized by low deposition temperature, high deposition rate, relatively low operational cost and high-energy process capabilities due to the nature of arc plasma discharge.
The direct current (D.C.) and pulsed current vacuum arc comprise two approaches implemented for film deposition. Compared with D.C. arc, pulsed arc has the advantages of higher ion energies and higher deposition rate as well as the reduction of macro droplets intrinsically associated with the cathodic arc process. However, two main issues limit the utilization of vacuum arc on silicon material. One is that the arc cannot be initiated on the intrinsic silicon unless it is heavily doped or is heated to increase the intrinsic electric conductivity substantially. The other problem with silicon is low thermal conductivity compared with most metals. The local heating at cathode spots and the resulting thermal shock can cause the silicon target to crack. Previous reports of cathodic vacuum arc on silicon film deposition were focused on the D.C. arc operation only. Pulsed technology is more appropriate for silicon cathodic arc deposition.
Compared with the D.C. arc process, more uniform target erosion and better control of the silicon spots were achieved by adjusting the pulsed arc current parameters. The deposition rate was high at 0.2nm/A.s in comparison with other available technologies. The microstructure of the films was dense with polycrystalline macro droplets embedded in an amorphous silicon matrix. |
Frontier Carbon Materials Dr. Yap leads a very focused effort in the atomic bonding control of frontier carbon materials. The majority of his time is specifically spent improving recent innovations in the field such as growing carbon-nitride crystals at 800C and 15 atm. Approximately half of Dr. Yap’s work could be classified as highly theoretical with a 10-15 year discovery horizon and the other half being directed in the general direction of a more near term application (5 year horizon). |
MEMS Center in Wireless Integrated Microsystems A multi-university National Engineering Research Center in Wireless Integrated Microsystems funded by the National Science Foundation gives MTU a strong base for microtechnology research. Among its first projects, the center will design a next generation cochlear implant for which MTU will design and build a |
Dislocation Physics Laboratory The Dislocation Physics Laboratory conducts studies regarding the influences of dislocations on physical properties of solids.
The Laboratory focuses on three research areas: Investigating dislocation dynamics in semiconductors and intermetallics;
Understanding the basic mechanisms responsible for selective dislocation etching of semiconductors and intermetallics by RIE plasmas and chemical solutions;
Studying the fundamental processes in dislocation engineering of materials for new high-tech applications.
The Laboratory is equipped with several special facilities. Pulse Loading Systems apply stresses to move dislocations in samples of different materials. The systems can operate over a wide range of stresses, pulse durations and temperatures to measure the dislocation velocities in various materials under investigation.
A quartz annealing system equipped with an inert gas supply, high-temperature furnace, and programmed controller can reduce, if necessary, the density of dislocations, homogenize samples and/or stabilize their point defects. The individual dislocations are revealed by selective etching and observed by either an optical microscope with a PC-controlled digital camera, or an interferometric microscope, a scanning electron microscope, or an atomic force microscope.
The Reference Cell is a radio-frequency plasma discharge with a magnetically coupled sample manipulator. The Reference Cell, one of only several of this kind in the country, was specially designed for studying both the plasma properties and plasma etching of materials with different dislocation structures.
Several computer-controlled electronic systems and lasers allow measuring simultaneously properties of both plasmas and materials during etching. |
Electronic structure and transport properties of thermoelectric materials  This work is focused on computational condensed matter physics and materials science, in particular the electronic structure problem in semiconductors and complex materials. Computers are used as powerful microscopes to investigate the quantum properties that technology exploits to build new solid state devices. Solar cells, lasers and IR-detectors use semiconductor materials that are created ad hoc to optimize functions like light emission and detection. The research is aimed at optimizing the interesting properties of these materials by performing both semi-empirical and first principles calculations. |
Numerical Speedup Using Flowpaths  Applications for computer simulations include many research areas such as weather prediction, tracking the location and concentrations of contaminants in groundwater, oil recovery, studying disease processes, designing experiments, and developing medications. In these and several other applications, it is desirable to achieve speedup of numerical code. Current work in speeding up numerical simulations has several disadvantages. Considering the various disadvantages of each method, project will develop methods that increases the speed and (1) does not require rewriting an existing algorithm, although could be improved even further by making minor coding modification, (2) does not require algorithms written in traditional languages to be rewritten in other language, (3) executes portions of the code in parallel but does not suffer from the overhead of either a single microprocessor or multi-processor architecture, and (4)does not require time and effort to engineer and implement a special circuit for different types of numerical algorithms. This work proposes to develop such a technology using flowpaths where, starting with a C (or potentially FORTRAN) description of a numerical algorithm, a compiler will generate an executable that can be downloaded and will run on the Power PC embedded in an FPGA with parallel flowpaths to speedup the bottleneck loops in the numerical algorithm automatically.
With such a speed-up, some simulations that require real-time execution that can not currently be achieved by a PC will be able to run at a higher speed and achieve a real-time pace. The success of this research will result in future investigation including deriving optimizations for the compiler and resulting circuits, improving numerical schemes for optimal implementation in hardware and enhancing the compiler to support other popular languages.
The intellectual merit of this research project from a scientific computational standpoint lies in the discovery of new coding techniques that make optimal use of flowpaths in order to achieve higher simulation speeds. The intellectual merit in hardware design for speedup lies in the unique use of flowpaths for creating special-purpose processors for new and existing numerical code, automatically. This project serves as a novel interdisciplinary approach, combining expertise in scientific computation of numerical algorithms and high-speed embedded systems for significantly increasing the performance of numerical code, with impact both in software as well as in hardware technologies. |
The Least-Squares Meshfree Particle Finite Element Method Although the finite element method has been astonishingly successful in solving various problems in engineering and science, it has significant drawbacks: mesh generation and remeshing are very difficult and time-consuming. Meshfree methods may avoid these difficulties by constructing approximation functions entirely in terms of a set of nodes. Most meshfree methods are based on the Galerkin principle and employ moving least-squares approximation for the construction of shape functions. Although there is no need for an explicit mesh in the construction of moving least-squares shape functions, a separate background mesh is required to integrate the weak form, so they are not truly meshfree methods. Due to the non-interpolative character of the moving least-squares approximation, the enforcement of essential boundary conditions in the Galerkin formulation is quite awkward. Moreover, the moving least-squares approximation is more expensive computationally than the finite element interpolation. In the proposed research, we will develop a least-squares meshfree particle finite element method which combines the features of the least-squares finite element method and the meshfree particle method. The least-squares finite element method (LSFEM), based on minimization of the L2 norm of the residuals of a first-order system of differential equations, is a simple, efficient and robust technique, and can solve almost any kind of partial differential equation with the same mathematical/computational formulation. Since the least-squares method doesn't make use of the integration by parts for converting domain integration into boundary integration, and the meshfree particle method employs the usual finite element interpolations based on particles, all troubles that plague the Garlerkin-based meshfree methods disappear. The least-squares meshfree particle finite element method always leads to a symmetric positive definite system of linear algebraic equations. The matrix-free particle-by-particle conjugate gradient method can be used to solve very large problems on parallel computers, and the implementation is straightforward..
The purpose of this project is to develop a new computer method to simulate complicated engineering designs and sophisticated multi-physical processes with much greater accuracy and efficiency. Achievements of this project would enable numerical simulations beyond current capabilities in many important applications of national interest, including car crash safety analysis, noise reduction of cars, energy efficiency in full cells, heat reduction in semiconductor devices, etc. |
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