以Si3N4作增透膜的Si基Ge量子点探测器的研究

设计并制作了以Si3N4作增透膜的Si基Ge量子点红外探测器.采用气态源分子束外延(GSMBE)方法在Si(100)衬底上生长了20层的自组织Ge量子点.在此基础上,流水制作了p-i-n结构的量子点红外探测器.为了提高探测器的响应度,采用Si3N4作为增透膜以增强探测器对入射光的吸收.用传输矩阵方法模拟的结果显示,185上nm厚的Si3N4增透膜可以使探测器在1310 nm波长处具有较高的吸收率.根据此结果,用等离子体增强化学气相沉积(PECVD)方法在探测器表面淀积了185 nm的Si3N4.在室温下,测得量子点探测器在1.31μm处的响应度为8.5 mA/W,跟没有增透膜的器件相比,响应度提高了将近30倍.     

新的PIN型0.95μm光探测器设计

提出并设计了一种新的PIN型0.95μm光探测器。它的I层是Ge_0.3Si_0.7(8nm)/Si(12 nm),共50个周期。上、下缓冲层厚各为0.1μm,n~+-Si(10~(20)Cm~(-3)厚约0.5μm,衬底为〈100〉P~+-Si,器件面积为4mm~2。这种探测器一旦实现,它对0.95μm光的灵敏度比硅PIN型探测器高得多,可用于火灾报警等场合。     

P+PIN结构的650 nm光电探测器的研究

研究了一种新型P PIN结构的硅650 nm光电探测器,采用N型硅衬底,经过氧化光刻后,先作一次很薄淡硼扩散,再进行浓硼扩散,这样形成高低发射结的方法,减薄死层厚度,减少光生载流子的复合,提高了光电转换效率,从而使光谱响应度从普通650 nm光电探测器的0.30 A/W提高到了0.380 A/W,且具有约279 MHz的较高响应速度.     

基于退火效应硒化铅融合量子点制备及探测器性能研究

硒化铅纳米结构材料因其多激子产生效应、快速光敏吸收和近红外发射而被广泛应用于太阳能电池和光电探测器，并成为探测器领域的研究热点。在制备硒化铅量子点的基础上，通过退火工艺得到了一种新型的纳米材料融合量子点。所需的最佳退火温度可以有效减少缺陷，提高融合量子点的活性。为了体现融合量子点与其他材料相比的优势，采用旋涂法制备薄膜并用于光电导器件的研制。退火温度从室温提高到470℃,通过透射电子显微镜观察了不同温度下硒化铅量子点的融合现象，并研究了量子点退火对光电导器件性能的影响。量子点之间的平均距离随着退火温度的升高而减小，这增强了量子点之间的相互融合。实验数据表明，硒化铅活性层的最佳退火温度为310℃,开关比K和响应度R在310℃时达到最大值，响应度增加3倍以上。这是因为硒化铅活性层中载流子的迁移率增强。并成功制备了光电导探测器Au/PbSe融合量子点/Au(100 nm),为后续制备新的量子点器件奠定了基础。     

量子点红外焦平面读出电路接口研究及选择

目前InGaAs等材料的短波红外探测器读出电路已经较为成熟，其输入级接口电路也因不同公司和项目需求有着相对成熟的选择，但是在量子点短波红外探测器读出电路输入级接口电路的选择上，现有可查阅的公司及团队也并没有对输入级接口电路的选择进行研究，为了解决量子点探测器与读出电路输入级接口的匹配问题，对量子点探测器所使用的主流读出电路输入级结构进行研究，如CTIA、BDI,通过建立其电路等效模型并进行详细分析，以注入效率为切入点进行公式的研究与推导，将量子点探测器测试所得IV、CV分别结合不同输入级电路结构进行计算及对比，选择出一个更适合量子点探测器的读出电路输入级结构，最终选择CTIA型电路作为量子点短波红外探测器读出电路的输入级接口，其注入效率大于99%。     

基于低缺陷ZnO电子传输层的PbS量子点光电探测器研究

PbS胶体量子点因其光吸收系数高、制备成本低、沉积工艺简单、带隙可调等优点,成为备受关注的新型红外探测纳米材料。光电二极管结构的PbS量子点光电探测器通常使用高透过率、高电子迁移率的ZnO来制备N型层,以加快光生载流子的分离和提取。但是通过溶胶-凝胶法制备的ZnO薄膜在制备过程中会在薄膜中产生缺陷,限制ZnO层性能的发挥。本文通过调节ZnO前驱体溶液的浓度成功制备出缺陷更低的ZnO薄膜并应用于ZnO/PbS光电探测器件,经测试,当溶液浓度为0.7M(mol/L)时,所制备的器件表现出最佳的性能,在1 600 nm处的响应度和探测率分别为0.32A/W和3.48×10¹¹Jones,外量子效率为25%,器件的响应时间为τ_R=130μs,τ_F=20μs。这项工作为PbS量子点光电器件性能的优化提供了新的解决方案。     

氩氧比对ZnO薄膜特性的影响与紫外探测器的研制

利用射频磁控溅射技术在SiO2／n—Si和玻璃衬底上制备ZnO薄膜,研究了溅射气体氩氧比对薄膜特性的影响,在氩氧比为2：3下所制备的ZnO薄膜c轴择优取向相对较好,薄膜的颗粒随氩氧比的增加而增大,所制备的薄膜在可见光均具有较高的透射率,吸收边在360-380nm附近;并在以SiO。／n—Si为衬底,氩氧比为2：3,经过退火处理的ZnO薄膜上制作Ag-ZnO—Ag肖特基MSM叉指结构的紫外探测器,所制作的探测器在5V偏压下漏电流为3．3×10^-8A,在紫外波段有较高的响应度,光响应度峰值在365nm附近。     

退火对ZnO薄膜特性的影响与紫外探测器的研制

利用射频磁控溅射技术在SiO2/n-Si和石英玻璃衬底上制备了具有C轴择优取向的ZnO薄膜,研究了退火对ZnO薄膜特性的影响,并在以SiO2/n-Si为衬底、退火温度为900℃的薄膜上制作了Ag-ZnO-Ag肖特基型和Au-ZnO-Au光电导型MSM叉指结构的紫外探测器。所制作的两种MSM紫外探测器在350 nm波长紫外光照下电流增加,在紫外波段有较高的响应度,光响应度峰值在370 nm附近。     

利用3ω法同时测量Nd:YAG晶体及其表面SiO2/ZrO2增透膜导热系数

建立了适用于高频测量的3ω测试系统.对于薄膜/衬底复合结构,在低频范围内采用斜率-求差-3ω法,同时确定了单层薄膜和衬底的导热系数.采用低频和高频测量相结合的方法测量了Nd:YAG晶体和(111)面上微/纳米ZrO2/SiO2多层增透薄膜中各层的导热系数.进行了不确定度分析.建立的测量原理和测试系统可用于基体表面多层薄膜以及微纳米器件热物性的表征.     

16位InSb-SiCCD混合式红外CCD器件

<正> 本文报导16位n沟InSb-SiCCD混合式红外CCD器件,采用的是在P-InSb衬底上液相外延n-InSb层上制作n~+p结准平面型光伏探测器与n沟四相16位表面沟硅CCD多路传输器     

IR uncooled bolometers based on amorphous Ge/sub x/Si/sub 1-x/O/sub y/ on silicon micromachined structures

In this work, we present the fabrication of bulk micromachined microbolometers made of amorphous germanium-silicon-oxygen compounds (Ge/sub x/Si/sub 1-x/O/sub y/) grown by reactive sputtering of a Ge/sub 0.85/Si/sub 0.15/ target. We describe the complete procedure for fabricating thermally isolated microbolometers consisting of Ge/sub x/Si/sub 1-x/O/sub y/ sensing films deposited on sputtered silicon dioxide membranes suspended over a silicon substrate. The electrical properties of the sensitive material are set by controlling the deposition parameters of the sputtering technique. Under optimum deposition conditions, Ge/sub x/Si/sub 1-x/O/sub y/ layers with moderate electrical resistivity and thermal coefficient at room temperature as high as -4.2% /spl middot/ K/sup -1/ can be obtained. Isolated structures measured at atmospheric pressure in air have a thermal conductance of 3 /spl times/ 10/sup -6/ W /spl middot/ K/sup -1/ and a thermal capacitance of 6/spl middot/10/sup -9/ W /spl middot/ s /spl middot/ K/sup -1/, yielding a response time of 1.8 ms. Bolometers with an IR responsivity of 380 V /spl middot/ W/sup -1/ and a NEDT of 3.85 K at 100 nA bias current are obtained. The use of sputtered films allows designing a fully low-temperature fabrication process, wholly compatible with silicon integrated circuit technologies.     

Wafer direct bonding with ambient pressure plasma activation

Ambient pressure plasma processes were applied for surface activation of semiconductor (Si, Ge and GaAs) and other wafers (glass) before direct wafer bonding for MEMS and engineered substrates. Surface properties of activated wafers were analysed. Caused by activation high bond energies were obtained for homogeneous (e.g. Si/Si) as well as for heterogeneous material combinations (for instance Si/Ge) after a subsequent low temperature annealing process at 200°C. The resulting bond energies are analogous or higher as obtained for low-pressure plasma activation processes. The advantages of the ambient pressure plasma processes are described; a technical solution is discussed demonstrating the low risk for contamination and radiation damage.     

Germanium as a versatile material for low-temperaturemicromachining

Though germanium (Ge) shares many similar physical properties with silicon (Si), it also possesses unique characteristics that are complementary to those of Si. The advantages of Ge include its compatibility with Si microfabrication, its excellent gas and liquid phase etch selectivity to other materials commonly used in Si micromachining, and its low deposition temperature (<350°C) that potentially allows Ge to be used after the completion of a standard CMOS run. Wider applications of Ge as a structural, sacrificial, and sensor material require a more systematic investigation of its processing and properties. The results of such an undertaking are presently reported. The topics covered are the formation of Ge thin films and novel application of the selective deposition of Ge to etch hole filling, characterization of the effects of thermal treatment on the evolution of the residual stress in Ge thin films, etch selectivity for etch mask and sacrificial layer applications, and gas phase release technique for stiction elimination     

Thermodynamic and surface properties of liquid Ge–Si alloys

In the present work, the surface tension of liquid Si and Ge has been measured by the pendant/sessile drop combined method over the temperature range of 1723–1908 K and 1233–1313 K, respectively. The new surface tension data, the molar volumes and the melting temperatures of silicon and germanium as well as the excess Gibbs energy data of the Ge–Si liquid phase are the inputs for Calphad type modelling to study the mixing behaviour in alloy melts. The energetics of mixing in liquid Ge–Si system has been analysed through the study of the concentration dependence of various thermodynamic (activity, enthalpy of mixing, Gibbs energy of mixing), surface (surface tension and surface composition) and transport (diffusivity) properties as well as the microscopic functions (concentration fluctuations in the long-wavelength limit and chemical short-range order parameter) in the framework of statistical mechanical theory in conjunction with the Quasi-Lattice Theory (QLT).     

Amplification of fluorescence emission of CdSe/ZnS QDs entrapped in a sol-gel matrix, a new approach for detection of trace level of PAHs

In this work, CdSe/ZnS core/shell QDs with emission wavelengths of 535 nm, 545 nm, 555 nm and 575 nm were synthesized and the ligands on their surface were exchanged with mercaptopropionic acid (MPA) to make them water-soluble. Hydrophilic QDs were incorporated into a sol-gel GA matrix of 3-aminopropyl trimethoxysilane (APTMS) and 3-glycidoxypropyl trimethoxysilane (GPTMS) to fabricate QD-entrapped membranes. The fluorescence intensity of the QDs entrapped in the sol-gel membrane was increased after being activated by the energy transfer from polycyclic aromatic hydrocarbon compounds (PAHs). The signal increase of the QDs was proportional to the increase in the concentration of the PAHs. Herein, trace levels of anthracene (ANT), phenanthrene (PHE) and pyrene (PYR) were detected through the enhancement of the fluorescence intensity of the CdSe/ZnS QD-entrapped membranes. The linear detection ranges were 0.01-0.1 μM for ANT and PHE and 0.005-0.05 μM for PYR. The QD-entrapped sol-gel membranes also showed quite good stability for the detection of PAHs over a period of 2 months.     

Automatic segmentation of clustered quantum dots based on improved watershed transformation

Automated analysis of the quantum dots (QDs) images is very important in the field of material science. In this frame, efficient QDs segmentation is prerequisite. In this paper, we propose an algorithm of automatic detection and segmentation of the QDs, especially the clustered ones. We depend on fuzzy c-means (FCM) method for initial segmentation of the QDs from the substrate background. Then we present a modified watershed algorithm with markers and a novel marking function. The markers are extracted by adaptive H-minima transformation. Then a marking function based on Quasi-Euclidean distance transform is introduced to accurately and rapidly separate the clustered QDs. We demonstrate the comparisons of our method with the existing approaches. The experimental results show that the proposed method is efficient and accurate with very little running time and has a high quality on QDs segmentation.     

Red light emission from hybrid organic/inorganic quantum dot AC light emitting displays

An alternating current electroluminescent display has been direct written onto a flexible plastic substrate. A hybrid layer of poly(2-methoxy,5(2-ethylhexyloxy)-p-phenylene vinylene) (MEH-PPV) and CdSe quantum dots (QDs) were used to convert the light emitted by electroluminescent ZnS phosphor into red light. The emission wavelength of the display is found to be directly related to the emission of CdSe quantum dots. The integration of QDs into thin film electroluminescent (TFEL) displays has the potential to enhance its color spectrum.     

Carbon nanotube based sensors for the detection of viruses

Carbon nanotube biosensors were assembled using a layer-by-layer (LBL) technique exploiting the chemical functionalization on nanotubes to tailor their interactions with viruses and antiviral antibodies. Gold electrodes were patterned in the form of resistors onto a Si/SiO₂ substrate, followed by stepwise LBL assembly to change the resistivity of the channel. Polyelectrolyte multilayer films were prepared by the sequential electrostatic adsorption of poly(diallyldimethylammonium chloride), poly(styrene sulfonate), and functionalized single-walled carbon nanotubes. Viral antibodies were successfully immobilized between the electrodes and the binding of antibodies to the surface was enhanced by coating with poly(l-lysine). An antigen specific to the immobilized antibody was captured on these devices. The coupled antibody-antigen complex changed the conductance of the device and this change was related to the antigen concentration. The two factors affecting the performance of the device were the number of layers and the channel length between the electrodes. We were able to detect conductance change for a viral antigen with a titer of 10² TCID₅₀/ml (50% tissue culture infective dose).     

A droplet-based microfluidic platform for rapid immobilization of quantum dots on individual magnetic microbeads

Quantum dots (QDs) provide opportunities for the development of bioassays, biosensors, and drug delivery strategies. Decoration of the surface of QDs offers unique functions such as resistance to non-specific adsorption, selective binding to target molecules, and cellular uptake. The quality of decoration has substantial impact on the functionality of modified QDs. Single-phase microfluidic devices have been demonstrated for decorating QDs with biological molecules. The device substrate can serve as a solid-phase reaction platform, with a limitation being difficulty in the realization of reproducible decoration at high density of coverage of QDs. Magnetic beads (MBs) have been explored as an alternative form of solid-phase reaction platform for decorating QDs. As one example, controlled decoration to achieve unusually high density can be realized by first coating MBs with QDs, followed by the addition of molecules such as DNA oligonucleotides. Uniformity and high density of coatings on QDs have been obtained using MBs for solid-phase reactions in bulk solution, with the further advantage that the MBs offer simplification of procedural steps such as purification. This study explores the use of a droplet microfluidic platform to achieve solid-phase decoration of MBs with QDs, offering control of local reaction conditions beyond that available in bulk solution reactions. A microchannel network with a two-junction in-series configuration was designed and optimized to co-encapsulate one single 1 µm MB and many QDs into individual droplets. The microdroplet became the reaction vessel, and enhanced conjugation through the confined environment and fast mixing. A high density of QDs was coated onto the surface of single MB even when using a low concentration of QDs. This approach quickly produced decorated MBs, and significantly reduced QD waste, ameliorating the need to remove excess QDs. The methodology offers a degree of precision to control conjugation processes that cannot be attained in bulk synthesis methods. The proposed droplet microfluidic design can be widely adopted for nanomaterial synthesis using solid-phase assays.