Documents disponibles écrits par cet auteur

Controller and estimator design for regulation of film thickness, surface roughness, and porosity in a multiscale thin film growth process / Xinyu Zhang in Industrial & engineering chemistry research, Vol. 49 N° 17 (Septembre 1, 2010) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 49 N° 17 (Septembre 1, 2010) . - pp 7795–7806 Titre : Controller and estimator design for regulation of film thickness, surface roughness, and porosity in a multiscale thin film growth process Type de document : texte imprimé Auteurs : Xinyu Zhang, Auteur ; Gangshi Hu, Auteur ; Gerassimos Orkoulas, Auteur Année de publication : 2010 Article en page(s) : pp 7795–7806 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Estimator  Growth  process. Résumé : This work focuses on simultaneous regulation of film thickness, surface roughness, and porosity in a multiscale model of a thin film growth process using the inlet precursor concentration as the manipulated input. Specifically, under the assumption of continuum, a partial differential equation model is first derived to describe the dynamics of the precursor concentration in the gas phase. The thin film growth process is modeled via a microscopic kinetic Monte Carlo simulation model on a triangular lattice with vacancies and overhangs allowed to develop inside the film. Closed-form dynamic models of the thin film surface profile and porosity are developed and used as the basis for the design of model predictive control algorithms to simultaneously regulate film thickness, surface roughness, and porosity. Both state feedback and porosity estimation-based output feedback control algorithms are presented. Simulation results demonstrate the applicability and effectiveness of the proposed modeling and control approach by applying the proposed controllers to the multiscale model of the thin film growth process. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901396g [article] Controller and estimator design for regulation of film thickness, surface roughness, and porosity in a multiscale thin film growth process [texte imprimé] / Xinyu Zhang, Auteur ; Gangshi Hu, Auteur ; Gerassimos Orkoulas, Auteur . - 2010 . - pp 7795–7806. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 49 N° 17 (Septembre 1, 2010) . - pp 7795–7806 Mots-clés : Estimator  Growth  process. Résumé : This work focuses on simultaneous regulation of film thickness, surface roughness, and porosity in a multiscale model of a thin film growth process using the inlet precursor concentration as the manipulated input. Specifically, under the assumption of continuum, a partial differential equation model is first derived to describe the dynamics of the precursor concentration in the gas phase. The thin film growth process is modeled via a microscopic kinetic Monte Carlo simulation model on a triangular lattice with vacancies and overhangs allowed to develop inside the film. Closed-form dynamic models of the thin film surface profile and porosity are developed and used as the basis for the design of model predictive control algorithms to simultaneously regulate film thickness, surface roughness, and porosity. Both state feedback and porosity estimation-based output feedback control algorithms are presented. Simulation results demonstrate the applicability and effectiveness of the proposed modeling and control approach by applying the proposed controllers to the multiscale model of the thin film growth process. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901396g

Multivariable Model Predictive Control of Thin Film Surface Roughness and Slope for Light Trapping Optimization / Xinyu Zhang in Industrial & engineering chemistry research, Vol. 49 N° 21 (Novembre 2010) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 49 N° 21 (Novembre 2010) . - pp. 10510-10516 Titre : Multivariable Model Predictive Control of Thin Film Surface Roughness and Slope for Light Trapping Optimization Type de document : texte imprimé Auteurs : Xinyu Zhang, Auteur ; Gangshi Hu, Auteur ; Gerassimos Orkoulas, Auteur Année de publication : 2011 Article en page(s) : pp. 10510-10516 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Optimization  Trapping  Roughness  Thin  film  Predictive  control  Modeling Résumé : This work focuses on the development of a multivariable model predictive controller that simultaneously regulates thin film surface roughness and mean slope to optimize light reflectance and transmittance during thin film manufacturing by manipulating substrate temperature and deposition rate. Surface roughness and surface slope are defined as the root-mean-squares of the surface height profile and the surface slope profile, respectively. The dynamics of the evolution of the thin film surface height profile are assumed to be described by an Edwards-Wilkinson-type equation (a second-order stochastic partial differential equation) in two spatial dimensions. Analytical solutions of the expected surface roughness and surface slope are obtained on the basis of the Edwards-Wilkinson equation and are used in the controller design. The model parameters of the Edwards-Wilkinson equation depend on the substrate temperature and deposition rate. This dependence is used in the formulation of the predictive controller to predict the influence of the control action on the surface roughness and slope at the end of the growth process. The model predictive controller involves constraints on the magnitude and rate of change of the control action and optimizes a cost that involves penalty on both surface roughness and mean slope from the set-point values. The controller is applied to the two-dimensional Edwards-Wilkinson equation and is shown to successfully regulate surface roughness and mean slope to set-point values at the end of the deposition that yield desired film reflectance and transmittance. ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=23447943 [article] Multivariable Model Predictive Control of Thin Film Surface Roughness and Slope for Light Trapping Optimization [texte imprimé] / Xinyu Zhang, Auteur ; Gangshi Hu, Auteur ; Gerassimos Orkoulas, Auteur . - 2011 . - pp. 10510-10516. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 49 N° 21 (Novembre 2010) . - pp. 10510-10516 Mots-clés : Optimization  Trapping  Roughness  Thin  film  Predictive  control  Modeling Résumé : This work focuses on the development of a multivariable model predictive controller that simultaneously regulates thin film surface roughness and mean slope to optimize light reflectance and transmittance during thin film manufacturing by manipulating substrate temperature and deposition rate. Surface roughness and surface slope are defined as the root-mean-squares of the surface height profile and the surface slope profile, respectively. The dynamics of the evolution of the thin film surface height profile are assumed to be described by an Edwards-Wilkinson-type equation (a second-order stochastic partial differential equation) in two spatial dimensions. Analytical solutions of the expected surface roughness and surface slope are obtained on the basis of the Edwards-Wilkinson equation and are used in the controller design. The model parameters of the Edwards-Wilkinson equation depend on the substrate temperature and deposition rate. This dependence is used in the formulation of the predictive controller to predict the influence of the control action on the surface roughness and slope at the end of the growth process. The model predictive controller involves constraints on the magnitude and rate of change of the control action and optimizes a cost that involves penalty on both surface roughness and mean slope from the set-point values. The controller is applied to the two-dimensional Edwards-Wilkinson equation and is shown to successfully regulate surface roughness and mean slope to set-point values at the end of the deposition that yield desired film reflectance and transmittance. ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=23447943

Stochastic modeling and simultaneous regulation of surface roughness and porosity in thin film deposition / Gangshi Hu in Industrial & engineering chemistry research, Vol. 48 N° 14 (Juillet 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N° 14 (Juillet 2009) . - pp. 6690–6700 Titre : Stochastic modeling and simultaneous regulation of surface roughness and porosity in thin film deposition Type de document : texte imprimé Auteurs : Gangshi Hu, Auteur ; Gerassimos Orkoulas, Auteur ; Panagiotis D. Christofides, Auteur Année de publication : 2009 Article en page(s) : pp. 6690–6700 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Surface  roughness  Porosity  Thin  film  deposition  Kinetic  Monte  Carlo  simulation  Microscopic  model Résumé : This work focuses on stochastic modeling and simultaneous regulation of surface roughness and porosity for a porous thin film deposition process modeled via kinetic Monte Carlo (kMC) simulation on a triangular lattice. The microscopic model of the thin film growth process includes adsorption and migration processes. Vacancies and overhangs are allowed inside the film for the purpose of modeling thin film porosity. The definition of the surface height profile is first introduced for a porous thin film deposition taking place in a triangular lattice. The dynamics of surface height of the thin film are described by an Edwards-Wilkinson (EW) type equation, which is a second-order linear stochastic partial differential equation (PDE). The root-mean-square (RMS) surface roughness is chosen as one of the controlled variables. Subsequently, an appropriate definition of film site occupancy ratio (SOR) is introduced to represent the extent of porosity inside the film and is chosen as the second to-be-controlled variable. A deterministic ordinary differential equation (ODE) model is postulated to describe the time evolution of the film SOR. The coefficients of the EW equation of surface height and of the deterministic ODE model of the film SOR are estimated on the basis of data obtained from the kMC simulator of the deposition process using least-squares methods, and their dependence on substrate temperature is determined. The developed dynamic models are used as the basis for the design of a model predictive control algorithm that includes a penalty on the deviation of the surface roughness square and film SOR from their respective set-point values. Simulation results demonstrate the applicability and effectiveness of the proposed modeling and control approach in the context of the deposition process under consideration. When simultaneous control of surface roughness and porosity is carried out, a balanced trade-off is obtained in the closed-loop system between the two control objectives of surface roughness and porosity regulation. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900708v [article] Stochastic modeling and simultaneous regulation of surface roughness and porosity in thin film deposition [texte imprimé] / Gangshi Hu, Auteur ; Gerassimos Orkoulas, Auteur ; Panagiotis D. Christofides, Auteur . - 2009 . - pp. 6690–6700. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N° 14 (Juillet 2009) . - pp. 6690–6700 Mots-clés : Surface  roughness  Porosity  Thin  film  deposition  Kinetic  Monte  Carlo  simulation  Microscopic  model Résumé : This work focuses on stochastic modeling and simultaneous regulation of surface roughness and porosity for a porous thin film deposition process modeled via kinetic Monte Carlo (kMC) simulation on a triangular lattice. The microscopic model of the thin film growth process includes adsorption and migration processes. Vacancies and overhangs are allowed inside the film for the purpose of modeling thin film porosity. The definition of the surface height profile is first introduced for a porous thin film deposition taking place in a triangular lattice. The dynamics of surface height of the thin film are described by an Edwards-Wilkinson (EW) type equation, which is a second-order linear stochastic partial differential equation (PDE). The root-mean-square (RMS) surface roughness is chosen as one of the controlled variables. Subsequently, an appropriate definition of film site occupancy ratio (SOR) is introduced to represent the extent of porosity inside the film and is chosen as the second to-be-controlled variable. A deterministic ordinary differential equation (ODE) model is postulated to describe the time evolution of the film SOR. The coefficients of the EW equation of surface height and of the deterministic ODE model of the film SOR are estimated on the basis of data obtained from the kMC simulator of the deposition process using least-squares methods, and their dependence on substrate temperature is determined. The developed dynamic models are used as the basis for the design of a model predictive control algorithm that includes a penalty on the deviation of the surface roughness square and film SOR from their respective set-point values. Simulation results demonstrate the applicability and effectiveness of the proposed modeling and control approach in the context of the deposition process under consideration. When simultaneous control of surface roughness and porosity is carried out, a balanced trade-off is obtained in the closed-loop system between the two control objectives of surface roughness and porosity regulation. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900708v