West University of Timisoara

Blv. V Parvan 4, Timisoara 300223, Romania   http://www.uvt.ro 

Research

Modern engineering needs of crystals with specified size for use as final products without additional machining. Moreover, the quality of a crystal depends on the distribution of both special added and detrimental impurities.  A non-uniform distribution of such impurities along the crystal length and cross-section leads to non-uniform spatial, electrical and optical properties of the crystal.  Variations of the concentration of impurities along the crystal length and cross-section are determined by the processes that take place during the crystal manufacturing.

 

Mathematical models constructed for describing the evolution of the shape of the crystal and/or the distribution of impurities take into account such processes.

 

Objectives:

· Study of the dependence of the crystal shape on the pulling rate, melt temperature at the meniscus base, pressure in the furnace, vertical temperature gradient in the furnace, in view of the choice of the optimal process parameters.

· Develop and apply realistic mathematical models and numerical simulations, following permanent comparison between numerical results and experimental data, for growth methods in which the crystal shape is depending on a liquid meniscus: Edge-defined film-fed growth (EFG); Czochralski (Cz); Dewetted Bridgman (DW); Floating zone (FZ).

· Stability and control of the monocrystal shape and dopant distribution.

 

For these complex and rigorous explorations, mathematical and numerical tools are used in order to obtain theoretical and numerical results comparable with experimental data.

 

The numerical studies are performed using the following software:

· COMSOL Multiphysics for coupling different application modes which use partial differential equations: Navier-Stokes, Convection-Diffusion, Moving Mesh, etc.

· MathCAD and Mathematica for simulate the shape of the meniscus, the shape of the crystal and for other numerical data concerning the control, the regions of attractions, etc.

· Table Curve 2D and 3D for fitting the obtained numerical data.

 

Fluid flow in the meniscus and dependence of the dopant distribution

on the pulling rate in the case of the EFG technique

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Research grants

 

· Project coordinator of international program “Hubert Curien (PHC) - Brancusi”, Bilateral cooperation between Romania and France, NATIONAL AUTHORITY FOR SCIENTIFIC RESEARCH (NASR) grant: Mathematical and computational modelling of crystal growth processes based on capillarity, 2009-2010, Code 19550 PK.

· Project coordinator of Romanian PN-II–IDEI, THE NATIONAL UNIVERSITY RESEARCH COUNCIL (NURC) grant:  Modeling of the Dewetted Bridgman crystal growth process—control of the monocrystal shape and dopant distribution, 2009-2011, NURC Code 131.

· Project coordinator from partner country, NATO PROGRAMME SECURITY THROUGH SCIENCE COLLABORATIVE LINKAGE GRANT:  Evaluation and control of impurities in rapid-detection sensors, EAP.CLG. 982530/2007-2009; Project coordinator from a NATO country:  Thomas F, George, Office of the Chancellor, University of Missouri-St. Louis, St. Louis, MO 63121, USA.

· Project coordinator PN-II-RU-MC-2007-1, Mass transfer analysis in the case of a Nd:YVO4 cylindrical bar grown from the melt by the edge-defined film-fed growth (EFG) method, 2007, Cod CNCSIS 8.

· Project coordinator PN-II-RU-MC-2007-2, Arbitrary Lagrangian-Eulerian method for coupled Navier-Stokes and convection-diffusion equations with moving boundaries, 2007, Cod CNCSIS 243.

· Member of Romanian PNCDI2 - Program4: New models of natural calculus in the complex study and in solving of the complex problems, 2007-2010, Coordinator from partner West University of Timisoara: Assoc. Prof. Daniela Zaharie.

· Member of Romanian CNCSIS grant: Study of the nonlinear systems of ordinary differential equations which govern the motion of the spacecrafts and the high-speed fighters 2005-2007, Coordinator: Prof. Dr. Stefan Balint.

· Member of Romanian Space Agency (ROSA) grant: Modeling of the growth processes from the melt under the terrestrial and micro gravitational conditions, No. 170/2005, Coordinator: Prof. Dr. Stefan Balint.

· Member of European research grant Eurohomogenization (HMS) HPRN-CT-2000-00109, 2000-2004.

· Member of Romanian CNCSIS grant: Qualitative and numerical studies for the dynamical systems described by differential equations in finite and infinite dimensional spaces No.34964/2001, No.33475/2002, No.33960/2003, Coordinator: Prof. Dr. Stefan Balint.

· Member of Multi Universitary Research Institute (MURI) financed by USA, 1999-2000.