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High electronic density is achieved by polarization doping without an impurity dopant in graded AIGaN films. Low specific contact resistance is studied on the polarization-doped A1GaN/GaN heterojunctions by using the transmission line method (TLM). The sheet density of polarization-doped A1GaN/GaN heterojunction is 6 × 10 14 cm-2 at room temperature. The linearly graded material structure is demonstrated by X-ray diffraction. The cartier concentration and mobility are characterized by a temperature-dependent Hall measurement. Multiple-layer metal (Ti/A1/Ti/Au) is deposited and annealed at 650 ℃ to realize the Ohmic contacts on the graded A1GaN/GaN heterojunctions. 相似文献
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Homogeneous interface-type resistance switching in Au/La<sub>0.67</sub>Ca<sub>0.33</sub>MnO<sub>3</sub>/SrTiO<sub>3</sub>/F:SnO<sub>2</sub> heterojunction memories 下载免费PDF全文
La0.67Ca0.33MnO3 thin films are fabricated on fluorine-doped tin oxide conducting glass substrates by a pulsed laser deposition technique with SrTiO3 used as a buffer layer. The current-voltage characteristics of the heterojunctions exhibit an asymmetric and resistance switching behaviour. A homogeneous interface-type conduction mechanism is also reported using impedance spectroscopy. The spatial homogeneity of the charge carrier distribution leads to field- induced potential-barrier change at the Au-La0.67Ca0.33MnO3 interface and a concomitant resistance switching effect. The ratio of the high resistance state to the low resistance state is found to be as high as 1.3 × 10 4 % by simulating the AC electric field. This colossal resistance switching effect will greatly improve the signal-to-noise ratio in nonvolatile memory applications. 相似文献
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建立一种微波消解–石墨炉原子吸收光谱法测定露酒中铅的方法。样品蒸干后经微波消解前处理,然后用石墨炉原子吸收光谱法测定露酒中的铅的浓度,铅的浓度在0.0~20.0 ng/mL范围内呈良好的线性关系,线性相关系数为0.9996,取样2.00 mL定容至25.0 mL,得方法的检出限为0.003 mg/L,方法的定量限为0.010 mg/L。测定结果的相对标准偏差为3.4%~5.5%,加标回收率为88%~104%。该法具有灵敏度高,准确度、精密度良好,检测过程快速、省力等优点,适合日常批量检测。 相似文献
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以邻苯二胺(或4-甲基邻苯二胺)及一氯乙酸为原料,在酸性条件下,合成2-氯甲基苯并咪唑及2-氯甲基-5-甲基苯并咪唑;以取代羧酸为原料经酯化、肼解、再与CS2在氢氧化钾溶液中反应,合成10种2-巯基-5-取代-1,3,4-(口恶)二唑;将2种2-氯甲基-5-取代-苯并咪唑与10种2-巯基-5-取代-1,3,4-(口恶)二唑在氢氧化钠溶液中反应,合成14种2-[5’-CH3(H)-苯并咪唑-2’-亚甲硫基]-5-取代-1,3,4-(口恶)二唑衍生物.借助红外光谱、核磁共振氢谱和元素分析对化合物结构进行表征.初步生长素活性测试结果表明,所合成的化合物对小麦芽鞘和绿豆发芽有着不同程度的生长调节作用. 相似文献
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采用密度泛函理论(DFT)方法研究了碗状钒多酸阴离子[V12O32]4-、其碱金属阳离子衍生物[V12O32M]3-(M=Li,Na,K)及质子化衍生物的几何结构和二阶非线性光学(NLO)性质.结果表明,碱金属阳离子M+的引入对体系的几何结构和第一超极化率(β0)影响很小;而质子化的位置和取向对体系的几何结构和第一超极化率均有较大影响,与钒多酸阴离子[V12O32]4-相比,碗中部桥氧质子化体系的β0值增大,且比碗口处及碗底处桥氧质子化体系的β0值大270~400 a.u. 相似文献
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自费雪效应(假说)提出以来,通货膨胀率与股票收益率之间的关系引发了大量的争论,但二者之间的关系并无定论。本文利用门槛回归模型对通货膨胀率和股票收益率之间的关系进行的再检验,我们的研究发现:总体上,通货膨胀率和股票收益率表现为负相关,并且具有显著的门槛效应,当通货膨胀率较低或处于通货紧缩时,股票收益率和通货膨胀率之间存在不显著的负相关关系,而当通货膨胀率较高时,则表现为显著的负相关关系,呈现出明显的非对称性的特征,股票并不是抵御通货膨胀风险理想的保值品。此外,我们还对黄金类股票和黄金现货也进行了检验,研究表明,黄金现货与通货膨胀关系不显著,而黄金股收益率与沪深股市指数类似,与通货膨胀率具有显著的负相关关系,均非理想的抵御通胀保值品。 相似文献