化学氧化法聚吡咯导电性能与导电机理

采用化学氧化法制备了导电聚吡咯(PPy).运用SEM和TEM表征了PPy的形貌,利用四探针技术测试了材料的电导率,对影响其电导率的因素进行了讨论,并对其导电机理进行研究.结果表明,氧化剂用量、反应温度、反应时间、掺杂剂的种类等对最终所得材料的导电性能及结构形态有较大的影响.以苯磺酸钠作掺杂剂,FeCl3/Py摩尔比为1.0,冰浴条件下,反应0.5h所得材料电导率最高,为58.82S/cm,其中以2-萘磺酸为掺杂剂所得PPy微观形貌呈现罕见的纤维状.电导率相对较高的PPy,说明其本身掺杂状况使它在氧化掺杂时随导带和价带间的能级差减小,禁带变窄,载流子移动阻力小;阴离子的掺杂和脱掺杂变得容易,因而电导率高.     

Si-Ti-B掺杂金刚石/硬质合金复合体的性能

金刚石粒度和掺杂量两因素对Si-Ti-B掺杂金刚石/硬质合金复合体的金刚石层的抗弯强度和耐磨性的综合影响,可以归结为平均自由程与机械性能的关系。在强度(或耐磨性)与平均自由程的关系曲线中,存在最大值。对于低掺杂量材料,强度随平均自由程(粘结相层厚度)的减少而降低。对于高掺杂量材料,强度随粘结相层厚度的增大而下降。Si-Ti-B掺杂烧结金刚石的耐热性高于钴粘结金刚石。     

Numerical Simulation of Dopant Diffusion for Laser-Doped Crystalline Silicon

In this paper, the nonlinear numerical simulation of pulsed laser melting of crystalline silicon and phosphorus dopant liquid-phase diffusion has been established by the finite element method implemented in ANSYS. The melt front behavior as a function of time is described. The experimental SIMS work is intended to be used to validate the numerical model. The numerical simulation result is in good agreement with the corresponding experimental data.     

Depletion layer in pn-junction of diamond with phosphorus donor and boron acceptor

In order to understand characteristics of diamond pn-junction, ionized dopant and carrier profiles in pn-junction of diamond with phosphorus (P) donor and boron (B) acceptor are calculated. There exists a large transition region at a depletion layer edge due to Debye tailing at room temperature (RT). The length of Debye tailing, λ, is reduced with increasing compensation ratios and temperatures. The Debye tailing is predicted to facilitate an early effect of a pnp-bipolar transistor.     

Single Crystal Growth and Luminescent Properties of Na_5Eu(WO_4)_4

The single crystal growth of stoichiometric host luminescent crystal Na_5Eu(WO_4)_4 has been investigated.Using Na_2WO_4 as a flux,the optimum conditions to grow a pure single crystal by flux-slow-cooling methodhave been determined.A high optical quality single crystal of dimention 4.5 mm has been grown,which is thelargest one as we know so far.The micro-hardness of Na_5Eu(WO_4)_4 single crystal is 3.46×10~3 MPa.Itsrefractive index is 1.81 in white light wavelength region and the specific gravity is 5.65 g/cm~3.The fluorescentand excitation spectra have been determined and the reason of the fluorescent quench of ~5D_2 and ~5D_1 to ~7F_jof Eu~(3 )can be explained as multi-phonon non-radiation transition.     

Observation of indium-vacancy and indium-hydrogen interactions in Hg1−xCdxTe

We have used a nuclear hyperfine technique, perturbed γγ angular correlation (PAC), to study the interactions between¹¹¹In and native defects and impurities in Hg_1−xCd_xTe. The PAC technique uses the quadrupole interaction of¹¹¹In with local electric field gradients to characterize the local environment of this donor dopant. We observed that when In was diffused into a bulk or thin film sample of Hg_1−xCd_xTe (x=0.21 and x=0.3) at 350°C and the sample was slow cooled, the In occupied sites with near-cubic symmetry, presumably the substitutional metal site. However, when the sample was quenched, a fraction of the In was incorporated into defects characterized by quadrupole interaction strengthsv _Q1 andv _Q2 and asymmetries of ν₁=ν₂=0.08. These defects are attributed to the trapping of a metal vacancy at a next-nearest neighbor site to the In atom. The introduction of hydrogen by boiling the samples in distilled water for >4h eliminated the previously observed PAC signals and created defects characterized byv _Q3=35 MHz, ν₃ <0.1 andv _Q4=MHz, ν₄ <0.1. These defects are attributed to the decoration of the In-V_Hg complex by a hydrogen atom. Hall effect measurements showed that hydrogenation increased the hole concentration in p-type quenched samples and even converted n-type indium-doped samples to p-type. A possible model for hydrogen incorporation which includes self-compensation by vacancy creation is suggested.     

Electrochemical capacitance-voltage characterization of plasma-doped ultra-shallow junctions

Ultra-shallow Si p⁺n junctions formed by plasma doping are characterized by electrochemical capacitance-voltage (ECV). By comparing ECV results with those of secondary ion mass spectroscopy (SIMS), it is found that the dopant concentration profiles in heavily-doped p⁺ layer as well as junction depths measured by ECV are in good agreement with those measured by SIMS. However, the ECV measurement of dopant concentration in the underlying lightly doped n-type substrate is significantly influenced by the upper heavily-doped layer. The ECV technique is also easy to control and reproduce. The ECV results of ultra-shallow junctions (USJ) formed by plasma doping followed by different annealing processes show that ECV is capable of reliably characterizing a Si USJ with junction depth as low as 10 nm, and dopant concentration up to 10²¹ cm⁻³. Also, its depth resolution can be as fine as 1 nm. Therefore, it shows great potential in application for characterizing USJ in the sub-65 nm technology node CMOS devices. __________ Translated from Chinese Journal of Semiconductors, 2006, 27(11): 1966–1969 [译自: 半导体学报]     

Experimental and theoretical insights into sulfur resistance of transition metal-doped Cu–Fe spinel during chemical looping combustion

A series of transition-metal doped Cu–Fe spinel oxygen carriers (M-CuFe₂O₄, M = Mn, Cr, Co and Ni) were synthesized and examined for their sulfur resistance by 500 ppm H₂S in N₂ atmosphere. The results showed that H₂S vulcanized the M-CuFe₂O₄ surfaces and led to the generation of metal sulfide. The gaseous sulfur product was mainly SO₂. The interaction between sulfur and CuFe₂O₄ was weakened when doping transition-metal into Fe site of CuFe₂O₄, especially Cr as dopant. The increase of temperature had an obvious impact on the reaction between H₂S and the adsorbed oxygen species. Cr dopant reduced the enrichment of sulfur element on the surface, and it showed the weakest affinity towards sulfur because of the lowest orbital hybridization between S and Cr atom below the Fermi level. Moreover, the energies barriers of H₂S dissociation over Cr–CuFe₂O₄ surface were obviously higher than those over CuFe₂O₄.     

Feeding and egg-laying preferences of the sawtoothed grain beetle Oryzaephilus surinamensis: Beyond cereals and cereal products

The insect's response to various living substrates is an important determinant for their life history and demography reflected in their feeding and egg-laying preferences. However, research on polyphagous stored product insects such as the sawtoothed grain beetle, Oryzaephilus surinamensis (L.) (Coleoptera: Silvanidae), are largely focused on cereal grains neglecting its alternative hosts. Therefore, this study examines the effect of a range of 16 host substrates including dry fruits, nuts, oil and legume seeds on insect development, survival, and adult emergence of the sawtoothed grain beetle, besides of also determining the feeding substrate weight loss. Overall, the feeding substrates exhibited a significant and different effect on O. surinamensis, except egg incubation time and length of the pupal period. The longest larval periods were observed on legumes followed by oilseeds and (dry) fruits. The highest survival and adult emergence were recorded on fruits and nuts, except raisin, but significantly lower than when fed on legume seeds, including soybean. The losses in fruits and nuts were higher, particularly on almonds and cashew. Larva development was inversely correlated to survival and adult emergence, which were positively correlated to substrate loss. Our study indicated that several non-grain commodities such as (dry) fruits and nuts are rather suitable substrates for the population growth of O. surinamensis, an additional concern for in international trade.     

Polypyrrole based electro-conductive textiles for heat generation

This work deals with the preparation and characterization of electrically conductive textiles for heat generation. Needlepunched nonwoven, spunlace nonwoven, and woven fabrics, all made of 100% polyester fibers, were made electrically conductive by in situ chemical polymerization of pyrrole with p-toluene sulfonic acid dopant. Alkali hydrolysis of polyester fabrics was done before in situ polymerization for better fixation of polypyrrole on polyester. The average surface resistivities were found to be 1013.08, 1099.72, and 1434.12?Ω/□, respectively, for needlepunched, spunlace, and woven fabrics. The electro-conductive fabrics displayed exponential rise of surface temperature on application of voltage and the rise of temperature was found to be related to the time duration of applied voltage. The electro-conductive fabrics exhibited linear voltage–current relationship at low voltage range. The surface resistivity of the electro-conductive fabrics was increased substantially on prolong exposure to atmosphere.