BAND-STRUCTURE OF MG1-XZNXSYSE1-Y

The empirical pseudopotential method within the virtual crystal approximation is used to calculate the band structure of Mg1-xZnySySe1-y, which has recently been proved to be a potential semiconductor material for optoelectronic device applications in the blue spectral region. It is shown that MgZnSSe can be a direct or an indirect semiconductor depending on the alloy composition. Electron and hole effective masses are calculated for different compositions. Polynomial approximations are obtained for both the energy gap and the effective mass as functions of alloy composition at the GAMMA valley. This information will be useful for the future design of blue wavelength optoelectronic devices as well as for assessment of their properties.

Photoluminescence of ZnS clusters in zeolite-Y

Two obvious emissions are observed from the ZnS clusters encapsulated in zeolite-Y. The emission around 355 nm is sharp and weak, locating at the onset of the absorption edge. The band around 535 nm is broad, strong and Stokes-shifted. Both the two emissions shift to blue and their intensities firstly increase then decrease as the loading of ZnS in zeolite-Y or clusters size decreases. Through investigation, the former is attributed to the excitonic fluorescence, and the latter to the trapped luminescence from surface states. The cluster size-dependence of the luminescence may be explained qualitatively by considering both the carrier recombination and the nonradiative recombination rates. Four peaks appearing in the excitation spectra are assigned to the transitions of 1S-1S, 1S-1P, 1S-1D and surface state, respectively. The excitation spectra of the clusters do not coincide with their absorption spectra. The states splitted by quantum-size confinement are detected in the excitation spectra, but could not be differentiated in the optical absorption spectra due to inhomogeneous broadening. The size-dependence of the excitation spectra is similar to that of the absorption spectra. Both the excitation spectra of excitonic and of trapped emissions are similar, but change in relative intensity and shift in position are observed.

Room temperature continuous wave operation of 1.33-micron InAs/GaAs quantum dot laser with high output power

Continuous wave operation of a semiconductor laser diode based on five stacks of InAs quantum dots (QDs) embedded within strained InGaAs quantum wells as an active region is demonstrated. At room temperature, 355-mW output power at ground state of 1.33-1.35 microns for a 20-micron ridge-waveguide laser without facet coating is achieved. By optimizing the molecular beam epitaxy (MBE) growth conditions, the QD density per layer is raised to 4*10^(10) cm^(-2). The laser keeps lasing at ground state until the temperature reaches 65 Celsius degree.

用SF6—N2混合气的反应离子刻蚀制作WSix微米结构

于2010-11-23批量导入

Upconversion emission of a Er3+-doped glass microsphere under 633 nm excitation

In this work, The TBS glass microspheres doped with Er3+ for morphology-dependent resonances of upconversion emission were designed. The glass sample components are 25TiO(2)-27BaCO(3)-8Ba(NO3)(2)-6ZnO(2)-9CaCO(3)-5H(3)BO(3)-10SiO(2)-7water glass-3Er(2)O(3) (wt%), and the emission spectra of TBS glass and a TBS glass microsphere (about 48 mum in diameter) were measured under 633 nm excitation and discussed. The strong morphology-dependent resonances of upconversion luminescences in the microsphere were observed. The observed resonances could be assigned by using the well-known Lorenz-Mie Formalism. (C) 2003 Elsevier Ltd. All rights reserved.

长白山阔叶红松林生产力对气候变化响应的模拟研究

本论文以长白山阔叶红松林为研究对象，观测了阔叶红松林主要树种的光合生理生态特征，建立了单叶化汁卜片的光合作用模型，上推出群落的生产力模型，采用基于干物质生产过程的模型Sim-CYCLE，模型了该生态系统对·气候变化的响应。得到主要结论如下：（1）、在不同的CO2浓度和光合有效辐射条件下，长白山阔价卜红松林主要树种净光合速率月动态规律不同；气孔导度随着瞬时光合有效辐射强度和C02浓度的增加而有下降趋势。（2）、建立的适用于阔价f一红松林的单叶化气孔导度对环境因子气温（Ta）、光合有效辐射（PAR）、饱和水汽压（VPD）的响应模型：gs＝PAR（-1.606Ta2＋118.192Ta＋1878.67）／（355.700+PAR）（-430.433+VPL），这是一个基于叶片光合机理的群落生产力模型，在模拟了长白山阔叶红松林群落生产力时取得了满意的效果。（3）、采用干物质产量理论的Sim-CYCLE模型，通过样地尺度的参数化模拟表明，长白山阔叶红松林生态系统的总初级生产力（GPP）为14.89Mgcha-1、净初级生产力（NPP）为8.22MgCha-1、净生态系统生产力困EP）为2．67MgCha-1；在CO2倍增和温度上升时碳积累在增加，净初级生产力（NPP）为9.03±1.51MgCha-1、净生态系统生产力（NEP）为2.95±0.47MgCha-1。

长白山北坡灌木阔叶红松林定位动态分析

灌木阔叶红松林做为长白山地区的主要地域性顶极群落，其相对稳定程度一直受到有关人士的关注。笔者通过其固定标准地长期观测资料的分析，探讨其中龄林阶段、近熟林阶段、以及从中龄林演替到近熟林过程中，该类型森林生态系统的动态规律。首先，在中龄林（建群种红松的优势木年龄约为170年）阶段的十年动态规律是：在林冠层中，立木总株数显著增多，其中槭树和椴树株数激增现象尤为明显。枯倒木树种有限（仅四种），且大、中、小径级枯倒木株数比为3:5:15，中、小径级枯倒木多为砸倒木。种群平均胸径除槭树、椴树和榆树出现负增长外，余者均有所增大。立木树冠相对高度变化不明显，红松立木大多仍处于被压冠状态。总生物量由305.40吨/公顷增343.04公顷，其中各种群生物量均有不同程度的增加。十年中，因枯倒木而使其总生物量损失了9.18吨/公顷。群落更新状况不良。十年中更新幼苗幼树的保存率极低，且总株数由4775株/公顷降至3700株/公顷。其中红松更新尤为恶化。群落中灌木和草本植被的生物量，无论是地上部分还是地下部分，均略有增大趋势。在其土壤层中，浅层的发生有机养分富积现象显著。其降水和气温变化状况为：降水和温度的林、内外年变化规律正相关性较强，且林内均低于林外。降水和气温的年代变化规律不明显。其次，在近熟林（建群种红松的优势木年龄约为260年阶段其林冠层九年动态规律为：活立木总株数增加稀少，红松、蒙古栎和榆树的株数均保持相对而言稳定。枯树木树种较多（仅蒙古栎未发生枯倒），且大、中、小径级枯倒木株数之比为8：4：8，其中风倒和病腐枯倒木所占比重较大。各种群平均胸径和平均冠幅均有所增大。红松树冠具有冲破上层阔叶树冠进入林冠层上层的趋势。总蓄积具增大趋势，种群蓄积除白桦外均有所增大。总生物量由342.64吨/公顷增至355.45吨/公顷，其中槭树、椴树和白桦的生物量受枯倒木的影响，出现负增长现象。最后，群落由中龄林演替至近熟林过程中的动态规律是：在林冠层，活立木总株数减少趋势显著，但种群按株数多少排序的结构变化不大。枯倒木的树种有增多趋势，且其平均胸径由25.13厘米升至31.69厘米。种群平均胸径和平均冠幅均有增大趋势。总蓄积量505.34立米米/公顷升至524.00立方米/公顷。总生物量由343.04吨/公顷增至355.45吨/公顷，其平均年增长量有明显的趋势。在演替层，立木种类和株数均有减少趋势，使得结构较简单的演替层更趋于简单化。在该层中，未发现建群种红松的存在。总生物量由2.64吨/公顷降至2.44吨/公顷。在更新层，更新状况由不良趋于恶化。幼苗树总株数由3846株/公顷降至2946株/公顷，其中红松更新株数所占比重趋于减少至零。在灌木层，灌木总株数由6125株/公顷降至5575株/公顷，其中大灌木株数增多，而小灌木株数减少。毛榛子于灌木层中株数所占比重最大，由33%升至42%。总生物量由2.85吨/公顷升至4.85吨/公顷。在草本层中，草本植被的种类，总株数和总盖度均有增多或增大的趋势。总生物量由0.77吨/公顷升至1.04吨/公顷。群落的总生物量由349.28吨/公顷升至363.78吨/公顷。在土壤层中，有机养分在浅层的发生层中富积现象较显著，且其浅层发生层的酸度有减弱至趋于中性的趋势。本文的动态分析不仅为该林型动态数学模型的建立和检验提供了更为可靠的依据，同时对于其经营措施的制定具有一定的科学价值。