Recent research results on deep level defects in semi-insulating InP - Application to improve material quality

An apparent defect suppression effect has been observed in InP through an investigation of deep level defects in different semi-insulating (SI) InP materials. Quality improvement of SI-InP based on the defect suppression mechanism is presented.

子午岭地区植被演替过程中土壤养分及酶活性特征研究

选择植被自然恢复不同年限的阳坡梁坡地作为研究对象,采用时空互代法研究子午岭地区植被恢复过程中土壤养分和酶活性的变化。结果表明,植被恢复140 a内,不同土层土壤有机质含量、全氮含量、蔗糖酶活性、脲酶活性、碱性磷酸酶活性和过氧化氢酶活性增加,且表土层(0~20 cm)土壤养分含量和酶活性高于下层土壤(20~40 cm)。以裸露地为对照,土壤0~20 cm土层,有机质含量、全氮含量、蔗糖酶活性、脲酶活性、碱性磷酸酶活性和过氧化氢酶活性分别增加了23.8%~534.9%、9.3%~300.0%、213.6%~521.5%、40.4%~286.5%、22.7%~232.2%和3.2%~22.4%,土壤速效磷含量呈现波动变化,过氧化氢酶活性变化幅度比其他三种酶低。土壤有机质含量与全氮、速效磷含量密切相关;土壤蔗糖酶与土壤有机质、全氮均为极显著的相关关系(0.930/0.918);土壤脲酶活性与全氮含量相关系数最高(0.804);土壤碱性磷酸酶活性与有机质、全氮含量都呈极显著相关(0.977/0.984);土壤过氧化氢酶活性与全氮含量极显著相关,相关系数达0.996。

不同培肥措施下种植制度及撂荒对土壤微生物量碳氮的影响

以黄土高原南部半湿润易旱区已进行17年的田间定位试验为研究对象,研究了不同培肥措施(不施肥、施用氮磷钾及氮磷钾与有机肥配合施用)下两种种植制度(一年1熟及一年两熟)和撂荒对土壤微生物量碳、氮(SMBC、SMBN)及可溶性有机碳、氮(SOC、SON)等含量的影响。结果表明,与一年1熟的小麦-休闲种植制度相比,一年两熟小麦-玉米轮作提高了0~10cm土层SMBC、SMBN、有机碳(TOC)、全氮(TN)和土壤SOC、SON的含量,而对10~20cm土层上述测定指标影响不大。与不施肥(CK)或单施化肥处理(NPK)下小麦-休闲和小麦-玉米轮作方式相比,撂荒处理显著提高了0~10cm土层各测定指标的含量。不同培肥措施相比,氮磷钾配施有机肥显著提高了0~10cm、10~20cm土层SMBC、SMBN含量;NPK处理0~10cm土层SMBN含量显著增加,10~20cm土层SMBN和0~10cm、10~20cm土层SMBC含量增加但未达显著水平。不同培肥措施和种植制度对SMBC/TOC和SMBN/TN的比例无明显影响。

Annealing ambient controlled deep defect formation in InP

Deep defects in annealed InP have been investigated by deep level transient capacitance spectroscopy (DLTS), photo induced current transient spectroscopy (PICTS) and thermally stimulated current spectroscopy (TSC). Both DLTS results of annealed semiconducting InP and PICTS and TSC results of annealed semi-insulating InP indicate that InP annealed in phosphorus ambient has five defects, while lid? annealed in iron phospbide ambient has two defects. Such a defect formation phenomenon is explained in terms of defect suppression by the iron atom diffusion process. The correlation of the defects and the nature of the defects in annealed InP are discussed based on the results.

Residual donors in undoped LEC InP

Undoped liquid encapsulated Czochralski (LEC) InP samples have been studied by Hall effect, glow discharge mass spectroscopy (GDMS) and infrared absorption spectroscopy. A systematic discrepancy has been found between the Han electron concentration and net donor concentration measured by GDMS. The electron concentration is always higher than the net shallow donor concentration by about (3-6)x10(15)cm(-3). A hydrogen indium vacancy complex donor defect VInH4 was detected regularly by infrared absorption spectroscopy in all undoped LEC InP samples. The fact can be explained by taking into account the existence of the donor defect in as-grown undoped LEC-InP.

Characterization of defects and whole wafer uniformity of annealed undoped semi-insulating InP wafers

Semi-insulating (SI) InP wafers of 2 and 3 in. diameters have been prepared by annealing undoped LEC InP at 930 degreesC for 80 h under pure phosphorus ambient (PP) and iron phosphide ambient (IP). The electrical uniformity of annealed undoped SI wafers, along with a Fe-doped as-grown SI LEC InP wafer, has been characterized by whole wafer PL mapping and radial Hall measurements. Defects in these wafers have been detected by photo-induced current transient spectroscopy (PICTS). The results indicated that the uniformity of IP wafer is much better than that of PP wafer and as-grown Fe-doped Si InP wafer. There are fewer traps in undoped SI InP IP wafer than in as grown Fe-doped and undoped SI InP PP wafer, as evidenced by PICTS. The good uniformity of the IP wafer is related to the nonexistence of high concentration of thermally induced defects. The mechanism for this phenomenon is discussed based on the results. (C) 2002 Elsevier Science B.V. All rights reserved.

InP-based optoelectronic devices for optical fiber communications

In this contribution we report the research and development of 1.55 mu m InGaAsP/InP gain-coupled DFB laser with an improved injection-carrier induced grating and of high performance 1.3 mu m and 1.55 mu m InGaAsP/InP FP and DFB lasers for communications. Long wavelength strained MQW laser diodes with a very low threshold current (7-10 mA) have been fabricated. Low pressure MOVPE technology has been employed for the preparation of the layered structure. A novel gain-coupled DFB laser structure with an improved injection-carrier modulated grating has been proposed and fabricated. The laser structures have been prepared by hybrid growth of MOVPE and LPE techniques and reasonably good characteristics have been achieved for resultant lasers. High performance 1.3 mu m and 1.55 mu m InGaAsP/InP DFB lasers have successfully been developed for CATV and trunk line optical fiber communication.

潜流人工湿地氮磷净化功能研究

人工湿地作为一种污水生态处理系统正在得到越来越广泛的应用，但是人工湿地的脱氮除磷能力还存在着观点上的分歧，本研究以生活污水和城市地表径流为处理对象，将小试研究与工程规模研究相结合，探讨了潜流人工湿地对废水中氮磷的净化功能和机制，开发了有效除氮的湿地新工艺，发现了影响基质除磷的关键因素，总结了基质优化选择的原则。 潜流人工湿地可以有效地处理生活污水和城市地表径流，TP在初期运行时的去除效率高，达80%以上，TN的去除率不超过60%；潜流人工湿地需要适合的一级处理，宜采用高水力负荷低污染负荷的运行方式； 潜流人工湿地内随深度增加还原性增强，随流向还原性减弱，湿地中氮磷污染物的浓度变化与氧化还原电位具有一定的相关性，各种湿地微生物的数量和分布与目标污染物的迁移转化存在着明显的相关性； 湿地植物对氮磷的吸收潜力很大，湿地植物比较适合的收割时期为枯萎前期，不影响植物的生长，又能去除更多的氮磷； 接触环境中6.6＜pH＜7.7条件下，决定基质除磷量的最关键因素是基质中Ca的含量；基质粒径会影响湿地除磷效率和除磷持久性，经济易得且Ca含量高的沙子和碎石是潜流人工湿地基质的首选； 景观型复合潜流人工湿地的开发使垂直流湿地和水平潜流湿地的优缺点可以得到互相补充，TN去除效率大幅提高，景观效果和生态价值得到提升。

人工湿地塘床系统净化污水的机理研究

人工湿地处理污水实验场经过多年的运行已形成了较稳定的具有多 种生物种类的适合污水处理的生态系统，活水公园人工湿地塘床系统运行时间仅一年，初步显示了湿地生态系统的生物多样性特点。筛选出了菖蒲、芦苇、茭白、香蒲、水竹、马蹄莲、凤眼莲、浮萍、睡莲等适合本地人工湿地塘床系统种植的湿地植物。人工湿地塘床系统是由各种湿地单元与各种各样的高、低等生物和所处的开放式的环境共同构成了较为完整的具有净化污水功能的生态系统，因此，与生物滤池相比，把人工湿地塘床系统称为生态滤池显得更为合适。其出水具有生物安全性。实验结果表明，实验场对生活污水中的COD_(Cr)、BOD_5、TP的去除率在80％以上，对TN的去除率为60.60% ～ 86.4%，细菌总数的去除率为86.9% ～ 99.6%，总大肠菌群的去除率为94.6% ～ 99.7%，其出水水质能够满足二级污水处理的要求。活水公园对枯水期府河水中的COD_(Cr)、BOD_5、TN、TP的去除率在85％以上，总大肠菌群的去除率为99.97%，其净化效果能够满足污水深度处理的需要。湿地植物光合作用向水体供氧能力的试验研究结果表明，在几种光照控制条件静态试验和现场试验中，菖蒲、香蒲、茭白、水竹、凤眼莲等植物植株水面以上的茎、叶在光照条件下进行光合作用时并没有引起根层区水体内溶解氧浓度的升高（氧增），反出现下降（氧亏）。说明这些植物水上部分光合作用对水体DO没有贡献。浮萍光合作时引起氧增的作用较弱，仅维持低水平，试验期间9:00 ～ 15:00的氧增幅度在0.11 ～ 1.13mg/L之间，平均为0.44mg/L。芦苇在9:00 ～ 15:00光合作用时根层区水体氧增幅在-0.20 ～ 1.07mg/L之间，平均为0.30mg/L。上述这些植物植株的水面以下的根、根茎、茎、叶如果暴露在光照条件下时，会进行光合作用，产生的氧直接释放到水体并引起氧增的作用非常明显，试验期间9:00 ～ 15:00的氧增幅度在1.91 ～ 16.1mg/L之间。人工湿地处理污水系统植物床基质内各测点的上、下层COD_(Cr)值虽有一定的差别，但经过成对平均数比较分析发现这种差别并未形成明显的趋势。污水在植物床基质中流动时，随着迁移距离的延长，其中的COD_(Cr)的降解速率呈现先快后慢的趋势，根据动态变化规律，建立了COD_(Cr)在植物床基质层内沿程水平迁移降解动态变化模型：C_L = C_o exp(4.629 * 10~(-5)L~2-0.01567L，0 ≤ L ≤ 100。经验证，模型预测值与实际监测值呈非常显著相关（r ≥ 0.9946 > r_(0.0005(4))，r_(0.0005(4)) = 0.9741)。在人工湿地塘床系统运行监测过程中，发现处于光照下的水体中的pH呈周期性变化，与DO的变化规律相似，在试验期间，9:00 ～ 15:00的pH和DO都呈上升趋势，两者呈协同周期性变化。经相关性回归分析，pH的变化规律与DO呈非常显著相正关，植物床表层渍水区pH与DO的回归关系相关系数r = 0.9129 > r_(0.01(70))(r_(0.01(70)) = 0.302)，植物塘内的pH与DO的相关系数r = 0.8584 > r_(0.01(60))(r_(0.01(60)) = 0.325)，植物床基质层内的pH与DO之间的相关性较差。相关分析结果表明，DO变化幅度大的水体中，pH的变化幅度也就越大，两者之间的相关性也就越显著，这可能与水体中氧化还原电位和水生植物光合作用伴随的代谢活动有关。这种相关性和协同周期性变化具有一定的生态学意义，并会给净化污水的效果产生影响。

黑土人工快速渗滤系统工艺参数筛选及净化功能

东北黑土区是我国主要粮食基地之一，水资源短缺和水环境污染问题严重；城市生活污水资源化堕待解决。本文根据污水土地处理技术，以黑土和石英砂为介质，采用室内模拟的方法，建立并运行了黑土人工快速渗滤系统。本文首次运用均匀设计原理，建立了以COD、TN、TP最大去除率和最大水力负荷为｝！标的优化工艺参数（人工土壤的组成、淹水时间、湿千比）筛选方法；并提出了以倒数方程来确定系统稳定的渗滤速度和稳定的COD、翎、TP去除率。在优化条件下，COD、TN、TP去除率和渗滤速度的理论结果分别为：85.02％、93.75％、92.62％和9.57cm/h；实际运行结果分别为：85.33％、93.01％、93.27％和9.26cm/h。表明此筛选方法是可行的。研究表明，在COD优化条件下可以实现COD（去除率=85.02％）和TP（去除率＝91.59％）共同有效地去除。加入草炭影响系统的净化效果。同时本文还研究了在优化条件下黑土人工快速渗滤系统Eh和微生物组成特征。黑土人工快速渗滤系统对LAs具有较强的净化能力，在＜100mg／L浓度条件下，LAS去除率在90％以上。LAS主要被吸附于20～40cm土层中；高浓度LAS会在系统中积累；延长干化时间可以提高系统对LAS的去除率。高浓度LAS会造成系统对其它污染物（cOD、TN、NH4+-N、TP，可溶性磷等）去除率的下降，造成Eh降低和微生物数量的减少等。

牦牛粪便对青藏高原东部高寒草甸土壤养分系统的影响

川西北高寒草甸位于青藏高原东部地区，是我国四大牧区之一，也是长江和黄河等江河源区的重要水源涵养功能区。近几十年来，大量牦牛粪便被牧民作为生物能源、肥料或者食用菌产业的原料而利用，为草原生态系统的养分平衡增加了生态风险。鉴于在青藏高原地区针对牦牛粪便的相关研究尚未见报道，本文从粪便和土壤养分相互变化趋势的角度出发，研究了粪便在夏秋两季的分解状况和粪便其下及其周围土壤的养分变化。通过此研究，将有助于了解牦牛粪便在自然状态下的分解速率以及粪便对土壤养分及土壤微生物生物量的影响，为粪便对草地土壤生态系统的贡献提供概念性认识，同时也为高寒草甸草地这种脆弱生态系统的可持续管理提供理论依据。 针对牦牛粪便自身养分释放及其对土壤在时间和空间尺度上的影响，本文通过模拟牛粪堆积，在不同时间和固定区域内对牛粪和土壤进行了夏秋两季的采样测定，分析了牛粪及土壤NO3--N、NH4+-N、速效K、无机P、有机C、全N 和全P 含量随时间的变化趋势。得到如下结果： 1. 在研究区域内，牛粪对草地生态系统具有较强的养分（N、P）贡献能力。据初步统计，其估值大致为氮素699~932 kg ha-1，P 素为110~147 kg ha-1。牛粪（湿重、干重）在夏秋季节的分解速率具有较大差异，夏季显著快于秋季。夏季牛粪湿重、干重在2 个月左右之后分别降为初期的14%和24%，而秋季同期分别降为35%和52%。牛粪养分（NO3--N、NH4+-N、速效K、无机P、有机C、全N 和全P）的分解速率在夏季也要显著快于秋季。秋季经过2 个月左右的分解之后，牛粪以上含量分别降至初始态的32%、60%、36%、64%、58%、63%和43%，远高于夏季的同期水平。 2. 在不同季节，牛粪周围的土壤养分（NO3--N、NH4+-N、速效K 和无机P）含量变化随时间改变呈现相同的趋势。但是，牛粪周围不同远近下土壤养分随时间的动态变化幅度略有不同。粪下土壤养分含量随时间变化波动较大，距粪便越远，随时间变化的变幅越为平缓。总体来说，在夏季由于粪便分解较快，对土壤养分的持续作用时间不及秋季，秋季粪便分解变慢，表现出养分的缓释特征。其次，牛粪对粪下土壤影响的持续时间也长于对周围土壤的作用时间。 3. 粪便对土壤养分（NO3--N、NH4+-N、速效K、无机P）影响的范围在不同季节具有差异。夏季要高于秋季，但对周围土壤养分影响的持续时间低于秋季。在夏季短期内，牛粪对土壤NO3--N 和速效K 含量的影响范围能够超过30cm，而对NH4+-N 和无机P 的影响范围则介于10cm 和30cm 之间。在2 个月左右之后，牛粪对周围土壤养分的影响能力基本消失。在秋季，牛粪对周围土壤养分影响范围难以达到30cm 处。粪便在夏季对其下土壤和周围土壤的有机C、全N 和全P 含量并无显著影响，但在秋季能显著增加其下土壤有机C、全N 和全P 含量。 4. 牛粪在秋季对土壤SMB-C、SMB-N 和SMB-P 含量的影响能够持续2 个月以上，由于秋冬季节牛粪分解缓慢，因此推断这种效应持续时间至少能够1 年左右。另一方面，牛粪在秋季对土壤SMB-C、SMB-N 和SMB-P 含量的影响范围主要集中在其下土壤，而周围的影响效应并不明显。 The grassland on the eastern fringe of Qinghai-Tibetan Plateau was one of the four greatest pasture zones in our country and the main water conservation function zones in the hesastream of Yangtse River and Huanghe river. Rencent years, lots of dung in this area was used as biological energy, fertilizer or material of fungoid growing, leading to high risk of nutrient banlance in grassland ecosystem. In view of the researches on the impact of yak dung in this area are relatively rare, the present study focused on the relationship of dung and soil nutrient transformation in sunmer and autumn, which could profoundly illuminate the mechanism of dung decomposition and the effect of dung on soil chemical properties and soil microbe biomass. The present study also contributed to a basic understand and provided scientific management in the high-frigid ecosystem. Decomposition of yak dung and its effect on soil chemical properties in eastern grassland of Qinghai-Tibetan Plateau were determined. The study simulated the real dung pats, took dung and soil samples at different time and fixed-point in summer and autumn. The samples were analysed for NO3--N, NH4+-N, available K, inorganic P, total organic C (TOC), total N (TN), total P (TP). It was concluded that: 1. In study area, the yak dung supplied to ecosystem substantial nutrient. It is estimated that the N contribution of dung was approximately 699~932 kg ha-1, P contribution was approximately 110~147 kg ha-1. The rate of yak decomposition was more rapid in summer than autumn, the wet and dry weight of yak decreased to 14% and 24% respectively after 2 months when dung excreted in summer, with 35% and 52% in autumn. The content of NO3--N、NH4+-N、available K、inorganic P、TOC、TN and TP in dung decomposed more rapid in summer too. After 2 months when dung excreted in autumn, the content of above nutrient decreased to 32%、60%、36%、64%、58%、63% and 43% respectively，which were significantly higher than summer. 2. The content of NO3--N、NH4+-N、available K and inorganic P in soil around dung had the same transformation trend in each season, whereas it was distinguishing at different gradient of distance from dung, the nutrient in soil below dung had the most significant change while the more far from dung, the less change in soil. It was concluded that the yak dung had prolong impacts on soil in autumn compared with summer, besides, it aslo showed that the yak dung had protract effect on soil below dung compared with soil around dung. 3. The yak dung had expansive impact on soil around dung in summer whereas had relatively short effect compared with autumn. In short-term at summer, there was a significant increase about the content of NO3--N and available K around 30cm radius from dung pat while the content of NH4+-N and inorganic P between 10cm to 30cm. After 2 months, the impact almost disappeared. In autumn, the effect was hard to reach 30cm. The yak dung had no significant effects on the content of TOC、TN and TP in soil below or around dung in summer whereas there was a obvious increase in soil below dung pat in autumn. 4. The duration of effect of yak dung on soil microbial biomass(SMB) C、N and P was at least 2 months, maybe even more than 1 year. On the other hand, the impact of dung on SMB-C、SMB-N and SMB-P mainly acted on soil below dung while no obious effect on soil around dung.

长江口南汇潮滩湿地污水处理系统的净化功能

2002年8月～12月对长江口南汇潮滩湿地处理系统对污水净化效果进行了研究,分析了潮滩沉积物中N、P含量变化及其与功能细菌含量间的关系,以及芦苇对污染物质的直接去除作用。结果表明:潮滩湿地对污水的净化效果显著,对TN、TP和COD的去除率分别达到94.06%,76.82%和92.47%;沉积物中N、P含量随样点与排污口间距离增大呈下降趋势;沉积物中NH4+—N、NO3-—N、DIP含量与功能细菌数量间呈良好的正相关;收割芦苇去除的N、P量分别只占全年排入湿地总量的2.201×10-5%、4.552×10-4%。潮滩湿地对污染物的去除主要通过:潮汐稀释转移,沉降,滩面沉积物吸附等物理过程和微生物分解等生物过程的综合作用,而潮滩植物的直接去除作用仅占很小部分。

城市地表径流人工湿地生态处理工程

以武汉市桃花岛塘和人工湿地组合生态处理系统为研究对象,探讨了该系统处理城市地表径流的初期调试运行,结果表明:塘和人工湿地组合生态系统可以有效的处理城市地表径流,该生态系统对各污染物的去除率分别为CODCr75.4%～79.1%、TP81.8%～84.3%、TN64.9%～69.8%、SS93.8%～94.7%;其中人工湿地对其进水中污染物CODCr、TP、TN、SS的去除率分别为60.7%～64.8%、73.4%～75.6%、43.2%～48.4%、60.3%～66.4%,污染去除负荷达到COD0.01kg/(m2d)。在无雨期该生态系统可以处理一部分城市生活污水,实现削减污染和保持系统稳定的双重功能。

二级串联人工湿地处理稠油污水的季节变化

选取不同材料做基质,芦苇为湿地植物,构建了1#和2#二级串联潜流式人工湿地系统,对稠油采出污水进行现场处理试验研究。考察了水力负荷分别为0.18和0.09m3/(m2.d)的1#和2#湿地,不同季节(夏季和冬季)情况下的运行效果。结果表明,夏季人工湿地对石油类、COD、BOD5、TN、SS的去除率分别为79.22%、81.20%、89.67%、87.61%和89.47%;冬季则达到77.57%、78.98%、79.05%、71.35%、89.88%。