共查询到19条相似文献,搜索用时 171 毫秒
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利用射频磁控溅射技术室温制备了铟镓锌氧(IGZO)薄膜,采用X射线衍射(XRD)表征薄膜的晶体结构,原子力显微镜(AFM)观察其表面形貌,分光光度计测量其透光率。结果表明:室温制备的IGZO薄膜为非晶态且薄膜表面均匀平整,可见光透射率大于80%。将室温制备的IGZO薄膜作为有源层,在低温(<200℃)条件下成功地制备了铟镓锌氧薄膜晶体管(a-IGZO TFT),获得的a-IGZO-TFT器件的场效应迁移率大于6.0 cm2.V-1.s-1,开关比约为107,阈值电压为1.2 V,亚阈值摆幅(S)约为0.9 V/dec,偏压应力测试a-IGZO TFT阈值电压随时间向右漂移。 相似文献
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基于金属电子气模型,进行了温度、压力对Au反射率变化影响的研究与分析。利用DAC装置开展了压力对Au反射率变化测量实验,以及激光加热的动态温升条件下温度对Au反射率变化测量实验,获得了探测光束波长为488 nm条件下,温度(室温至350 ℃)和压力(11 GPa范围内)对Au反射特性影响的实验结果。结果表明:在11 GPa压力范围内,与温度因素相比,压力对Au的反射率变化影响可忽略;Au对488 nm波长激光的反射率变化趋势为单调递增,变化幅值达约10%,且具有反射率与温度的一一对应特性。通过动高压加载下材料温度瞬态测量要求分析,认为基于Au在488 nm波长下的反射变化特性,可建立一种适用于动高压加载下低温段(低于1000 K)的瞬态测温方法,用于解决材料动高压领域的瞬态测温技术难点。 相似文献
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海参的超高压处理与传统的处理方法相比有许多优越性,具有十分广阔的应用前景。研究了超高压处理过程中压力(0.1~550 MPa)、保压时间(0~30 min)、温度(24~62 ℃)及保压方式对海参自溶酶活性的影响。在室温、保压20 min的条件下,200 MPa左右较低压力下酶活性降低,相对残存活性为88.25%;250 MPa较高压力下自溶酶被激活,酶活性为106.77%;550 MPa高压下酶活性最低为29.81%。自溶酶活性随保压时间和温度的增加先上升后下降;保压方式对自溶酶活性的影响不大。同时利用误差反向传播神经网络(Back Propagation Neural Network,BP人工神经网络),模拟了超高压钝酶效果,与实验结果比较,平均相对误差为0.9%,可以获得较好的预测结果。研究结果表明,在一定的压力、保压时间和温度下,酶被激活,其活性上升;而在一定的压力、保压时间和温度下,酶被钝化,活性降低。对优化海参超高压钝酶工艺具有一定的参考价值。 相似文献
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在高压低温(77 K)条件下,利用红宝石荧光测压方法,系统地研究了金刚石对顶砧装置中固态氩和4∶1甲醇-乙醇混合物的传压特性。通过测量不同位置上红宝石荧光R1线的频移,确定了样品室内的压力分布。实验结果表明:在0~16 GPa的压力范围内,固态氩介质中反映介质非均匀性程度的|Δp/p|<3%、σp/p<2%,均在室温静水压条件下所允许的范围之内。红宝石荧光R线除随压力变宽外,与常压的很相似,表明固态氩在高压低温条件下是良好的传压介质。与之相比,4∶1甲醇-乙醇介质在77 K低温下的传压特性明显差于固态氩,已不适合作传压介质。 相似文献
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本文利用太赫兹时域光谱技术测量了室温条件下无水L-天冬酰胺与L-天冬酰胺一水合物的光谱特征,发现二者存在显著的差异,并利用太赫兹时域光谱技术实时检测L-天冬酰胺一水合物受热脱水的动态过程.结果表明太赫兹波对晶体结构变化、含结晶水状况以及分子间弱相互作用敏感.结合差示扫描量热法与热重分析联用、傅里叶变换红外光谱、粉末X射线衍射等多种技术分别从热学性质、分子振动等方面进行了表征,进一步确认了太赫兹实验结果的可靠性.采用基于密度泛函理论(DFT)的第一性原理平面波赝势方法,结合广义梯度近似(GGA)下的PBE交换-关联泛函,对L-天冬酰胺一水合物进行模拟计算,对实验所得太赫兹光谱与分子结构以及相互作用间的关系进行了讨论分析. 相似文献
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Being the simplest element with just one electron and proton the electronic structure of a single Hydrogen atom is known exactly. However, this does not hold for the complex interplay between them in a solid and in particular not at high pressure that is known to alter the crystal as well as the electronic structure and eventually causes solid hydrogen to become metallic. In spite of intense research efforts the experimental realization of metallic hydrogen, as well as the theoretical determination of the crystal structure has remained elusive. Here we present a computational study showing that the distorted hexagonal P63/m structure is the most likely candidate for Phase III of solid hydrogen. We find that the pairing structure is very persistent and insulating over the whole pressure range, which suggests that metallization due to dissociation may precede eventual bandgap closure. Due to the fact that this not only resolve one of major disagreement between theory and experiment, but also excludes the conjectured existence of phonon-driven superconductivity in solid molecular hydrogen, our results involve a complete revision of the zero-temperature phase diagram of Phase III. 相似文献
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Noble metals adopt close-packed structures at ambient pressure and rarely undergo structural transformation at high pressures. Platinum (Pt) is normally considered to be unreactive and is therefore not expected to form hydrides under pressure. We predict that platinum hydride (PtH) has a lower enthalpy than its constituents solid Pt and molecular hydrogen at pressures above 21.5?GPa. PtH transforms to a hexagonal close-packed or face-centered cubic (fcc) structure between 70 and 80 GPa. Linear response calculations indicate that PtH is a superconductor at these pressures with a critical temperature of about 10-25?K. These findings help to shed light on recent observations of pressure-induced metallization and superconductivity in hydrogen-rich materials. We show that the formation of fcc noble metal hydrides under pressure is common and examine the possibility of superconductivity in these materials. 相似文献
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R. Rajeswarapalanichamy G. Sudha Priyanga M. Kavitha S. Puvaneswari K. Iyakutti 《Journal of Physics and Chemistry of Solids》2014
Ab initio calculations are performed to investigate the structural stability, electronic, structural and mechanical properties of 4d transition metal nitrides TMN (TM=Ru, Rh, Pd) for five different crystal structures, namely NaCl, CsCl, zinc blende, NiAs and wurtzite. Among the considered structures, zinc blende structure is found to be the most stable one among all three nitrides at normal pressure. A structural phase transition from ZB to NiAs phase is predicted at a pressure of 104 GPa, 50.5 GPa and 56 GPa for RuN, RhN and PdN respectively. The electronic structure reveals that these nitrides are metallic. The calculated elastic constants indicate that these nitrides are mechanically stable at ambient condition. 相似文献
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Börje Johansson 《Hyperfine Interactions》2000,128(1-3):41-66
The similarity and difference between the solid state properties of the 4f and 5f transition metals are pointed out. The heavier
5f elements show properties which have direct correspondence to the early 4f transition metals, suggesting a localized behaviour
of the 5f electrons for those metals. On the other hand, the fact that Pu metal has a 30% lower volume than its neighbour
heavier element, Am, suggests a tremendous difference in the properties of the 5f electrons for this element relative to the
heavier actinides. This change in behaviour between Pu and Am can be viewed as a Mott transition within the 5f shell as a
function of the atomic number Z. On the metallic 5f side of the Mott transition (i.e., early actinides), the elements show
most unusual crystal structures, the common feature being their low symmetry. An analogous behaviour for the lanthanides is
found in cerium metal under compression, where structures typical for the light actinides have been observed experimentally.
A generalized phase diagram for the actinides is shown to contain features comparable to the individual phase diagram of Ce
metal. The crystal structure behaviour of the lanthanides and heavier actinides is determined by the number of 5d (or 6d)
electrons in the metallic state, since for these elements the f electrons are localized and nonbonding. For the earlier actinide
metals electronic structure calculations - where the 5f orbitals are treated as part of the valence bands - account very well
for the observed ground state crystal structures. The distorted structures can be understood as Peierls distortions away from
the symmetric bcc structure and originate from strongly bonding 5f electrons occupying relatively narrow 5f states. High pressure
is an extremely useful experimental tool to demonstrate the interrelationship between the lanthanides and the actinides.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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Simple diatomic molecules exhibit a variety of exciting physical phenomena under high pressures, including structural transitions, pressure induced metallization, and superconductivity. Oxygen is of particular interest because it carries a magnetic moment. For the first time we studied the magnetic structure in solid oxygen under very high pressure by a direct method, namely, neutron diffraction. A new type of magnetic order with ferromagnetic stacking of the antiferromagnetic O2 planes was discovered in delta-O2 at P=6.2 GPa. We show that all structural transformations at pressures <7 GPa are driven by spin interactions; therefore, high-pressure oxygen should be considered as a unique "spin-controlled crystal." 相似文献
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Somayazulu M Madduri A Goncharov AF Tschauner O McMillan PF Mao HK Hemley RJ 《Physical review letters》2001,87(13):135504
Simple molecular solids become unstable at high pressures, typically transforming to dense framework and/or metallic structures. We report formation of an unusual ionic solid NO(+)NO(3)(-) (nitrosonium nitrate) from N(2)O at pressures above 20 GPa and temperatures above 1000 K. Synchrotron x-ray diffraction indicates that the compound crystallizes with a structure related to the aragonite form of CaCO(3) and NaNO(3). Raman and infrared spectroscopic data indicate that the structure is noncentrosymmetric and exhibits a strong pressure dependent charge transfer and orientational order. 相似文献
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Pressure-induced phase transitions in the ZrXY (X= Si,Ge, Sn;Y= S,Se, Te) family compounds 下载免费PDF全文
Pressure is an effective and clean way to modify the electronic structures of materials, cause structural phase transitions and even induce the emergence of superconductivity. Here, we predicted several new phases of the ZrXY family at high pressures using the crystal structures search method together with first-principle calculations. In particular, the ZrGeS compound undergoes an isosymmetric phase transition from P4/nmm-I to P4/nmm-II at approximately 82 GPa. Electronic band structures show that all the high-pressure phases are metallic. Among these new structures, P4/nmm-II ZrGeS and P4/mmm ZrGeSe can be quenched to ambient pressure with superconducting critical temperatures of approximately 8.1 K and 8.0 K, respectively. Our study provides a way to tune the structure, electronic properties, and superconducting behavior of topological materials through pressure. 相似文献