Size Control of Nanoscale Silicon Particles Formed in Thermally Annealed A-Si ： H Films and Its Photoluminescence

A method to control the size of nanoscale silicon grown in thermally annealed hydrogenated amorphous silicon （a-Si：H） films is reported. Using the characterizing techniques of micro-Raman scattering, X-ray diffraction and computer simulation, it is found that the sizes of the formed silicon particles change with the temperature rising rate in thermally annealing the a-Si ： H films. When the a-Si：H films have been annealed with high rising rate（～100℃/s）, the sizes of nanoscale silicon particles are in the range of 1.6～15nm. On the other hand, if the a-Si：H films have been annealed with low temperature rising rate（～1℃/s）, the sizes of nanoscale silicon particles are in the range of 23～46nm. Based on the theory of crystal nucleation and growth, the effect of temperature rising rate on the sizes of the formed silicon particles is discussed. Under high power laser irradiation, in situ nanocrystallization and subsequent nc-Si clusters are small enough for visible light emission, authors have not detected any visible photoluminescence（PL） from these nc-Si clusters before surface passivation. After electrochemical oxidization in hydrofluoric acid, however, intense red PL has been detected. Cyclic hydrofluoric oxidization and air exposure can cause subsequent blue shift in the red emission. The importance of surface passivation and quantum confinement in the visible emissions has been discussed.     

Electrochemical C-V Characteristics and Photoluminescence of a-C∶N Films

Amorphous carbon (a-C) films and amorphous carbon films incorporating with the nitrogen (a-C∶N) were deposited on silicon substrates in a radio-frequency driven plasma enhanced chemical vapour deposition system, while the surface electrical properties of films were investigated by electrochemical capacitance-voltage measurements. It was examined the effect of the interface defects on the properties and deduced that the conducting type of a-C∶N films was n-type. Subsequently, a comparative studies of a-C and a-C∶N films were performed by photoluminescence spectra depending on the temperature. With the decrease of the temperature, the main band with peak energy of 2.48 eV in the a-C∶N films was more intense compared with the other three bands caused by amorphous C in the a-C films.     

Statistics and Its Applications in Identification of Irregular Particles

Phase Doppler anemonetry(PDA)is very sensitive to the shape of testing particles,which is based on sphericity assumption and Mie‘s theory.In practice,there exists effectiveness of non-sphericity and the response of PDA system deviates from the theoretical prediction.In this paper,the statistic characteristics of PDA signal are analyzed and a method of inentifying and quantifying irregular particles is proposed.It is concluded that phase difference of PDA signal for irregular particles is an unbiased estimation for spherical particles.     

Mott and Efros–Shklovskii Variable-Range Hopping Conduction in Films Formed by Silicon Nanoparticles Doped with Phosphorus and Boron

Semiconductors - The electrical characteristics of thin films formed from Si nanoparticles (nc-Si) with various degrees of doping are studied. To eliminate the influence of ionic conduction, the...     

H ∞ and Robust Control of 2-D Systems in FM Second Model

This paper deals with output feedback stabilization and H control problems for two-dimensional (2-D) discrete linear systems without or with parameter uncertainty. The class of systems under investigation is described by the 2-D local state space Fornasini-Marchesini second model. We aim at designing a dynamical output feedback controller to achieve asymptotic stability and H performance for the 2-D system. It is shown that the design of output feedback controller can be recast into a convex optimization problem characterized by linear matrix inequalities (LMIs). The LMI solution is further extended to solve the robust stabilization problem for 2-D systems subject to norm-bounded uncertainty. The solutions for the H control and robust stabilization are applied to two application examples: thermal process control and robust stabilization of processes in Darboux equation.     

Stabilization of Discrete-Time Switched Systems with Input Time Delay and Its Applications in Networked Control Systems

In this paper, we focus on investigating the asymptotic stabilizability of switched systems with input time delay and its applications in networked control systems (NCSs). First, based on an important lemma, a linear matrix inequality (LMI)-based asymptotic stabilizability criterion is established. Stabilizing switched state feedback controllers can be designed by solving a set of LMIs, which can be easily tested with efficient LMI algorithms. Then, for NCSs with communication constraints, the NCS is modelled as a discrete-time switched system with input time delay. Thus, the asymptotic stabilizability criterion of switched system with input delay can be applicable to such NCSs. Finally, an example is given to illustrate our main results. This work is supported by the National Natural Science Foundation of China under grants (No. 60704015), a grant of Liuhui Center for Applied Mathematics of Nankai University and Tianjin University in China.