Papers by Keyword: Schottky Barrier

Abstract: (1-x)SnO₂-xZn₂SnO₄ composite ceramics were prepared by traditional ceramic processing and the varistor, dielectric properties were investigated. With increasing Zn₂SnO₄ content, the breakdown electrical field E_B and nonlinear coefficient α reaches the minimum of 6.9 V/mm and 2.5 at x=0.206, respectively. In the dielectric spectra, the relative dielectric constant ε_r exhibits strong frequency dependent character and at 40 Hz, ε_r for the sample of x=0.206 reaches a maximum as high as 3×10⁴. In the frequency region lower than 1 kHz, accompanied by the sharp increase of dielectric loss at 40 Hz, ε_r is depressed and a dielectric peak is presented in the spectra with increasing bias voltage. In the low electrical current range of 1.37-20 μA, The barrier height φ_B about 1.0 eV are obtained and it is found that φ_B decreases with increasing measuring current for each sample. Based on the results, the varistor behavior with high dielectric constant is explained by the Schottky barriers at grain boundaries.

Abstract: We have fabricated Au/CuPc/Al/CuPc/Au organic thin film transistor (OTFTs) using vacuum deposition with CuPc thin films of stable chemical property and semi conductive Al gate thin film electrode. The static and dynamic characteristics were tested at room temperature. The test results show that the switching speed of the OTFT is t_on=2.68ms, t_off= 1.32ms, amplification bandwidth is 400Hz, and the cutoff frequency f_c=400Hz when inputting 100Hz small square wave signal. Our OTFT has submicron conductive channel, shows operation characteristics of high frequency, high speed and high current density. Good static and dynamic characteristics of OTFT can be obtained by controlling appropriate Al gate film thickness and CuPc film thickness.

Abstract: The magnetic and electrical properties of Co/Ge bilayer films are experimentally studied. It is established that at the Co/Ge interface an intermediate magnetic layer forms. This layer affects the magnetic behavior and magnetoresistive effect in the investigated structures.

Abstract: Thin layers of tin oxide have numerous applications in various branches of microelectronics as transparent conductors and active elements in chemical sensors. While forming different metallic contacts to these layers are required for different applications, noble metals are of particular use in gas sensor fabrication as these devices operate at elevated temperatures and harsh environments. The background literature on the quality and electronic features of gold and silver contacts on SnO₂ layers is limited. Moreover, it has been shown that both gold and silver electrodes exhibit different electronic features on TiO₂ at different thermal and atmospheric conditions. Here, we report the I-V characteristics of Au/SnO₂ and Ag/SnO₂ contacts formed on SnO₂ layers deposited on SiO₂ substrates by ultrasonic spray pyrolysis. The obtained I-V plots proved the ohmicity of the Au/SnO₂ and Ag/SnO₂ contacts to be independent from the temperature, in the range of 300-700 K, and the composition of the surrounding atmosphere.

Abstract: Epitaxial graphene fabricated by thermal decomposition of the Si-face of silicon carbide (SiC) forms a defined interface to the SiC substrate. As-grown monolayer graphene with buffer layer establishes an ohmic interface even to low-doped (e. g. [N] ≈ 10¹⁵ cm^-3) SiC, and a specific contact resistance as low as ρ_C = 5.9×10^-6 Ωcm² can be achieved on highly n-doped SiC layers. After hydrogen intercalation of monolayer graphene, the so-called quasi-freestanding graphene forms a Schottky contact to n-type SiC with a Schottky barrier height of 1.5 eV as determined from C-V analysis and core level photoelectron spectroscopy (XPS). This value, however, strongly deviates from the respective value of less than 1 eV determined from I-V measurements. It was found from conductive atomic force microscopy (C-AFM) that the Schottky barrier is locally lowered on other crystal facets located at substrate step edges. For very small Schottky contacts, the barrier height extracted from I-V curves approaches the value of 1.5 eV from C-V and XPS.

Abstract: This paper reports the temperature dependent DC and RF characteristics of n-GaN Schottky diode simulated using Atlas/Blaze developed by Silvaco. It was found that as the temperature increases from 300K to 900K the forward current decreases due to lowering of the Schottky barrier with an increase in series-resistance and ideality factor. These observations indicates that tunneling behavior dominates the current flow rather than thermionic emission. Furthermore, the breakdown voltage decreases in reverse bias and insertion loss for RF behavior increases with respect to temperature due to the increase in capacitance near diode junction.Keywords: Atlas/Blaze, Schottky barrier, series resistance, ideality factor, insertion loss.

Abstract: Double-layered La_1.8Ca_1.2Mn₂O₇ sample with a perovskite structure was synthesized by solid state reaction and electrical transport properties were investigated using 4-wire direct current (DC) and 2-wire alternating current (AC) measurement methods. The result reveals that the I-V characteristic of the La_1.8Ca_1.2Mn₂O₇ ceramic exhibits a linear behaviour above Curie temperature (T_C) while it shows a strong nonlinearity below T_C. The nonlinear coefficient increases with decreasing temperatures and reaches a maximum of 60.5 at 14 K for the limit of the experiment. We believe that a magnetically correlated Schottky barrier forming at the grain boundary is the main factor to control the transport properties for the La_1.8Ca_1.2Mn₂O₇ ceramic.

Abstract: Nanocomposites of vertically aligned zinc oxide (ZnO) nanorod arrays incorporated with gold (Au) nanoparticles have been used as photoelectrodes to fabricate dye sensitized solar cells (DSSCs). Due to the surface plasmon resonance of the Au nanoparticles, the nanocomposite photoelectrodes demonstrate enhancement in the visible light absorption resulting in ~8% higher photocurrent compared to ZnO photoelectrode based DSSCs fabricated without any Au nanoparticles. In addition to the higher optical absorption due to the gold nanoparticles, a Schottky barrier forms at the ZnO/Au interface preventing the back electron transfer from the conduction band of the semiconductor nanorods to the redox electrolyte providing improvement in the charge separation at the nanocomposite photoelectrode. Upon incorporation of Au nanoparticles, the overall efficiency of the DSSC increased from 2.41% to 3.27%. The role of Au nanoparticles on the performance of the DSSCs for varying concentration of the Au nanoparticles as well as the post-growth annealing treatment of the nanocomposite photoelectrode is reported.

Abstract: The purpose of the paper is present the new result of electrical properties of Pt-doped silicon Schottky diodes that are fabricated by using CMOS technology. The results show the comparison of electrical properties namely current-voltage and capacitance characteristics between undoped and Pt-doped Schottky diode. The current characteristics of Pt-doped diode are decreased about 2 to 3 orders in term of reverse bias. As well as in case of forward bias, the current is slightly decreased. Schottky barrier height after Pt doping was increased from 0.84 eV to 0.86 eV. The built-in voltage of Pt-doped diodes was increased from 0.38 V to 0.42 V. The C-V characteristics after Pt doping is decreased about 5 pF. The change of electrical properties are caused by Pt because Pt atoms in silicon can occupy interstitial sites and change the trapping center. This paper will study and analyze the effect of Pt atom in silicon bulk of Schottky diode.

Abstract: The grain-boundary and its electrical characteristics in SrCoO₃doped ZnO varistors were studied. The grain-boundary around ZnO-grain is probably composed of SrCoO₃, and its electrical behavior is clearly different from two conventional types of Bi-and Pr-based ZnO varitors. The non-linearity and characteristic behavior could be explained by considering the n-p-n hetero-structure at the grain boundary. SrCoO₃ in the grain-boundary region should play crucial roles of not only the appearance of non-liner property but also the formation of different hetero-structure from double Schottky-barrier model on conventional varistors.