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51.
V. Svorcık J. Zehentner V. Rybka P. Slepicka V. Hnatowicz 《Applied Physics A: Materials Science & Processing》2002,75(4):541-544
Gold layers of increasing thicknesses were prepared on a polyethyleneterephthalate substrate by sputtering. The continuity
of a gold layer, as a function of the sputtering time, was examined using electron microscopy and by measuring its electrical
resistance and the reflection of electromagnetic microwaves. The mean layer thickness was determined from UV-VIS spectra as
well as from atomic absorption spectroscopy measurements of gold removed from a defined sample area. Layer thicknesses above
20 nm were also determined by a profilometer. These techniques enables one to characterize a transition of the gold layer
from a discontinuous one, through a continuous but inhomogeneous (thickness) one to a continuous and homogenous one.
Received: 2 August 2001 / Accepted: 6 September 2001 / Published online: 27 March 2002 相似文献
52.
Francisco Palacios Author Vitae Concepción Alonso Author VitaeAuthor Vitae Gloria Rubiales Author VitaeAuthor Vitae 《Tetrahedron》2007,63(3):523-575
Recent advances in the aza-Wittig reaction of phosphazene derivatives with several carbonyl compounds are reviewed. Phosphazenes afford inter- and intramolecular aza-Wittig reactions with different compounds such as aldehydes, ketones, esters, thioesters, amides, anhydrides and sulfimides. One of the most important applications of this reaction is the synthesis of a wide range of acyclic and heterocyclic compounds, ranging from simple monocyclic compounds to complex polycyclic and macrocyclic systems. 相似文献
53.
The current-voltage (I-V) characteristics of Al/p-Si Schottky barrier diodes (SBDs) with native insulator layer were measured in the temperature range of 150-375 K. The estimated zero-bias barrier height ΦB0 and the ideality factor n assuming thermionic emission (TE) theory show strong temperature dependence. Evaluation of the forward I-V data reveals an increase of zero-bias barrier height ΦB0 but decrease of ideality factor n with increase in temperature. The conventional Richardson plot exhibits non-linearity below 250 K with the linear portion corresponding to activation energy of 0.41 eV and Richardson constant (A*) value of 1.3 × 10−4 A cm−2 K−2 is determined from intercept at the ordinate of this experimental plot, which is much lower than the known value of 32 A cm2 K2 for holes in p-type Si. Such behavior is attributed to Schottky barrier inhomogene ties by assuming a Gaussian distribution of barrier heights (BHs) due to barrier height inhomogeneities that prevail at interface. Also, ΦB0 versus q/2kT plot was drawn to obtain evidence of a Gaussian distribution of the BHs, and values of ΦB0 = 1.055 eV and σ0 = 0.13 V for the mean BH and zero-bias standard deviation have been obtained from this plot, respectively. Thus, the modified versus q/kT plot gives ΦB0 and A* as 1.050 eV and 40.08 A cm−2 K−2, respectively, without using the temperature coefficient of the barrier height. This value of the Richardson constant 40.03 A cm−2 K−2 is very close to the theoretical value of 32 A K−2 cm−2 for p-type Si. Hence, it has been concluded that the temperature dependence of the forward I-V characteristics of the Al/p-Si Schottky barrier diodes with native insulator layer can be successfully explained on the basis of TE mechanism with a Gaussian distribution of the barrier heights. 相似文献
54.
Dynamical Analysis of Sputtering at Threshold Energy Range: Modelling of Ar+Ni(100) Collision System 下载免费PDF全文
The sputtering process of Ar+Ni(100) collision systems is investigated by means of constant energy molecular dynamics simulations. The Ni(100) slab is mimicked by an embedded-atom potential, and the interaction between the projectile and the surface is modelled by using the reparametrized ZBL potential. Ni atom emission from the lattice is analysed over the range of 20-50 eV collision energy. Sputtering yield, angular and energy distributions of the scattered Ar and of the sputtered Ni atoms are calculated, and compared to the available theoretical and experimental data. 相似文献
55.
Z.P. Shan S.M. Zhu W. Liu K. Tang H. Chen J.G. Liu Y.D. Zheng 《Applied Surface Science》2008,254(21):6962-6966
N-doped p-type ZnO (p ∼ 1018cm-3) was grown on sapphire(0 0 0 1) substrate by metal-organic chemical vapor deposition method. Ni/Au metal was evaporated on the ZnO film to form contacts. As-deposited contacts were rectifying while ohmic behavior was achieved after thermally annealing the contacts in nitrogen environment. Specific contact resistance was determined by circular transmission line method and a minimum specific contact resistance of 8 × 10−4 Ω cm2 was obtained for the sample annealed at 650 °C for 30 s. However, Hall effect measurements indicate that, as the rapid thermal annealing temperature increased up to 550 °C or higher the samples’ conductive type have changed from p-type to n-type, which may be due to the instability nature of the present-day p-type N-doped ZnO or the dissociation of ZnO caused by annealing process in N2 ambient. Evolution of the sample's electric characteristics and the increment of metal/semiconductor interface states induced by rapid thermal annealing process are supposed to be responsible for the improvement of electrical properties of Au/Ni/ZnO. 相似文献
56.
The current-voltage (I-V) characteristics of Al/SiO2/p-Si metal-insulator-semiconductor (MIS) Schottky diodes were measured at room temperature. In addition the capacitance-voltage (C-V) and conductance-voltage (G-V) measurements are studied at frequency range of 10 kHz-1 MHz. The higher value of ideality factor of 3.25 was attributed to the presence of an interfacial insulator layer between metal and semiconductor and the high density of interface states localized at Si/SiO2 interface. The density of interface states (Nss) distribution profile as a function of (Ess − Ev) was extracted from the forward bias I-V measurements by taking into account the bias dependence of the effective barrier height (Φe) at room temperature for the Schottky diode on the order of ≅4 × 1013 eV−1 cm−2. These high values of Nss were responsible for the non-ideal behaviour of I-V and C-V characteristics. Frequency dispersion in C-V and G-V can be interpreted only in terms of interface states. The Nss can follow the ac signal especially at low frequencies and yield an excess capacitance. Experimental results show that the I-V, C-V and G-V characteristics of SD are affected not only in Nss but also in series resistance (Rs), and the location of Nss and Rs has a significant on electrical characteristics of Schottky diodes. 相似文献
57.
Rogers SS Venema P van der Ploeg JP Sagis LM Donald AM van der Linden E 《The European physical journal. E, Soft matter》2005,18(2):207-217
In this article, a system of amyloid fibrils, based on the protein β-lactoglobulin, is studied by transient electric birefringence.
Single pulses of an electric field were applied to the solution, and the initial rise and subsequent decay of birefringence
analysed. The decay takes place on a range of relaxation times, and therefore contains information about the length distribution
of fibrils in the system. The information can be extracted using theories of the electric polarisability of polyelectrolyte
rods, since the fibrils are an example of these. Despite the long-standing complications of such theories, useful quantitative
information about the system can still be obtained. Using the Fixman model of polyelectrolyte polarisability, we obtain a
measurement of the short end of the length distribution which shows the fibril concentration as a function of length rising
linearly from 0.02-2 μm. The short end of the length distribution was unobtainable in our previous study using rheo-optics
(S.S. Rogers et al., Macromolecules 38, 2948 (2005)), but reasonable agreement between the two techniques shows they are complementary. 相似文献
58.
The current-voltage (I-V) and capacitance-voltage (C-V) characteristics of metal-insulator-semiconductor (Al/Si3N4/p-Si) Schottky barrier diodes (SBDs) were measured in the temperature range of 80-300 K. By using the thermionic emission (TE) theory, the zero-bias barrier height ΦB0 calculated from I-V characteristics was found to increase with increasing temperature. Such temperature dependence is an obvious disagreement with the negative temperature coefficient of the barrier height calculated from C-V characteristics. Also, the ideality factor decreases with increasing temperature, and especially the activation energy plot is nonlinear at low temperatures. Such behaviour is attributed to Schottky barrier inhomogeneties by assuming a Gaussian distribution of barrier heights (BHs) at interface. We attempted to draw a ΦB0 versus q/2kT plot to obtain evidence of a Gaussian distribution of the BHs, and the values of ΦBo = 0.826 eV and αo = 0.091 V for the mean barrier height and standard deviation at zero-bias, respectively, have been obtained from this plot. Thus, a modified ln(Io/T2) − q2σo2/2(kT)2 versus q/kT plot gives ΦB0 and Richardson constant A* as 0.820 eV and 30.273 A/cm2 K2, respectively, without using the temperature coefficient of the barrier height. This value of the Richardson constant 30.273 A/cm2 K2 is very close to the theoretical value of 32 A/cm2 K2 for p-type Si. Hence, it has been concluded that the temperature dependence of the forward I-V characteristics of the Al/Si3N4/p-Si Schottky barrier diodes can be successfully explained on the basis of TE mechanism with a Gaussian distribution of the barrier heights. In addition, the temperature dependence of energy distribution of interface state density (NSS) profiles was determined from the forward I-V measurements by taking into account the bias dependence of the effective barrier height and ideality factor. 相似文献
59.
Recent developments in asymmetric aziridination 总被引:1,自引:0,他引:1
Hélène Pellissier Author Vitae 《Tetrahedron》2010,66(8):1509-94
60.