Network technology has become a creative tool of changing human productivity, the rapid development of it has brought profound changes to our learning, working and life. Network technology has many advantages such as rich contents, various forms, convenient retrieval, timely communication and efficient combination of resources. Network information resources have become the new education resources, get more and more application in the education, has now become the teaching and learning tools. Network teaching enriches the teaching contents, changes teaching process from the traditional knowledge explanation into the new teaching process by establishing situation, independence and cooperation in the network technology platform. The teacher's role has shifted from teaching in classroom to how to guide students to learn better. Network environment only provides a good platform for the teaching, we can get a better teaching effect only by constantly improve the teaching content.
Changchun university of science and technology introduced a BB teaching platform, on the platform, the whole optical classroom teaching and the classroom teaching can be improved. Teachers make assignments online, students learn independently offline or the group learned cooperatively, this expands the time and space of teaching. Teachers use hypertext form related knowledge of applied optics, rich cases and learning resources, set up the network interactive platform, homework submission system, message board, etc. The teaching platform simulated the learning interest of students and strengthens the interaction in the teaching.
In this study, uniform InAs QDs were grown on the GaAs (001) substrate by MBE by the S-K mode. The effects of strain reducing layer and rapid thermal anneling on the optical properties of InAs/(In)GaAs QDs were investigated by PL measurements. The annealing results in PL peak energy red-shift which strongly depends on In composition of InxGaAs strained reducing layer , QDs with lower density and/or capped by an InGaAs layer are very sensitive to the annealing. At given annealing conditions, PL peak energy blue-shift of low-density QDs is much larger than that of high density QDs.
This paper describes a method for modelling film thickness variation across the deposition area within plasma enhanced
chemical vapour deposition (PECVD) processes. The model enables identification and optimization of film thickness
uniformity sensitivities to electrode configuration, temperature, deposition system design and gas flow distribution.
PECVD deposition utilizes a co-planar 300mm diameter electrodes with separate RF power matching to each electrode.
The system has capability to adjust electrode separation and electrode temperature as parameters to optimize
uniformity. Vacuum is achieved using dry pumping with real time control of butterfly valve position for active pressure
Comparison between theory and experiment is provided for PECVD of diamond-like-carbon (DLC) deposition onto flat
and curved substrate geometries. The process utilizes butane reactive feedstock with an argon carrier gas. Radiofrequency
plasma is used.
Deposited film thickness sensitivities to electrode geometry, plasma power density, pressure and gas flow distribution
are demonstrated. Use of modelling to optimise film thickness uniformity is demonstrated. Results show DLC
uniformity of 0.30% over a 200 mm flat zone diameter within overall electrode diameter of 300mm. Thickness
uniformity of 0.75% is demonstrated over a 200mm diameter for a non-conformal substrate geometry.
Use of the modelling method for PECVD using metal-organic chemical vapour deposition (MOCVD) feedstock is
demonstrated, specifically for deposition of silica films using metal-organic tetraethoxy-silane.
Excellent agreement between experimental and theory is demonstrated for conformal and non-conformal geometries.
The model is used to explore scalability of PECVD processes and trade-off against film thickness uniformity.
Application to MEMS, optical coatings and thin film photovoltaics is discussed.
High quality crack-free GaN layers were successfully grown and the InGaN/GaN based blue LEDs
fabricated on patterned Si (111) substrates. In addition to using the patterned growth technique, thin AlN and SiNx
interlayers grown at high temperatures were also employed to partially release the residual stress and to further
improve the crystalline quality. 300 µm square blue LEDs fabricated on the islands, without thinning and package,
exhibited a high output power of around 0.68 mW at a drive current of 20 mA.
The AlGaAs/GaAs double quantum well semiconductor lasers grown by molecular beam epitaxy show high
external quantum efficiency and high power conversion efficiency at continuous-wave power output using an
asymmetric structure. The threshold current density and slope efficiency of the device are 200A/cm2 and 1.25W/A,
respectively. The high external quantum efficiency and maximum conversion efficiency are 81% and 66%, respectively.
The characteristics of GaAs-based semiconductor Laser with antireflective and high reflective coatings are studied. The film designs are optimized with programmed software using the film design program for a double-layer scheme. According to the numerical simulations, the different double-layer with proper parameters is coated onto GaAs-based semiconductor Laser. The thickness of double layers is also calculated using the software taking account of antireflective and high reflective coating in the design of double layer film. With the optimized design of double-layer film, the power properties of GaAs-based semiconductor Laser are improved, and the experimental results satisfy the application requirements as semiconductor Laser.
The GaSb characteristics grown by molecular beam epitaxy (MBE) on GaAs substrates was reported. The abruptness of the interfaces, the degree of intermixing and the anion incorporation greatly affect the material quality. The RHEED patterns provide information on the surface structure and morphology of the sample and dictate surface reconstruction, accumulation and segregation. The structure parameters of samples are obtained from the rocking curve. The first and second satellite peaks appear around the main 0th-order peak. The experimental and simulated results of samples A and B with x-ray rocking curves show there is a GaAsSb layer because of As-for-Sb exchange at the GaSb/GaAs interface.
The temperature characteristics of Oxide-confined VCSEL are described, these records of high operating temperature are caused by high characteristic temperature. The VCSEL device temperature is increased by heating from ambient temperature 20°C up to 100°C. The effect of temperature elevation increased from T1 to T2 on the threshold current Ith(T) is often described by a characteristic temperature. We obtain a function T0(T) which decreases from 220K at 20°C temperature to 200K at 100°C. The essential improvements for the oxide-confined VCSEL in this work are focused on the following two points. First, we decrease the series resistance of the VCSEL. Secondly, the oxide-confined technique reduces defects and optical absorption in the active region. The oxide-confined is worthy to be used just because of its better confinements for both beam and current, easier processing, and lower cost. The fact that the device’s threshold current in pulse operation slightly depends on ambient temperature means that the VCSEL’s characteristic temperature (T0) is higher.