A detailed comparative study on the main electrical parameters of Au/n-Si and Au/PVA:Zn/n-Si Schottky barrier diodes

We have fabricated Au/n-Si and Au/PVA:Zn/n-Si Schottky barrier diodes (SBDs) to investigate the effect of organic interfacial layer on the main electrical characteristics. Zn doped poly(vinyl alcohol) (PVA:Zn) was successfully deposited on n-Si substrate by using the electrospinning system and surface morphology of PVA:Zn was presented by SEM images. The current–voltage (I–V) characteristics of these SBDs have been investigated at room temperature. The experimental results show that interfacial layer enhances the device performance in terms of ideality factor (n), zero-bias barrier height (Φ_B0), series resistance (R_s), and shunt resistance (R_sh) with values of 1.38, 0.75 eV, 97.64 Ω, and 203 MΩ whereas those of Au/n-Si SBD are found as 1.65, 0.62 eV, 164.15 Ω and 0.597 MΩ, respectively. Also, this interfacial layer at metal/semiconductor (M/S) interface leads to a decrease in the magnitude of leakage current and density of interface states (N_ss). The values of N_ss range from 1.36×10¹² at E_c—0.569 eV to 1.35×10¹³ eV^?1 cm^?2 at E_c—0.387 eV for Au/PVA:Zn/n-Si SBD and 3.34×10¹² at E_c—0.560 eV to 1.35×10¹³ eV^?1 cm^?2 at E_c—0.424 eV for Au/n-Si SBD. The analysis of experimental results reveals that the existence of PVA:Zn interfacial layer improves the performance of such devices.     

A comparative investigation of the oxidation of silicon using H2/O2, TCA/O2 and HCl/O2 mixtures

The oxidation of single-crystal silicon wafers has been investigated using an industrial thermal oxidation system. The growth characteristics and electrical properties of the oxides resulting from pure hydrogen/oxygen (H₂/O₂), trichloroethane/oxygen (TCA/O₂) and hydrogen chlorid/oxygen (HCl/O₂) mixtures have been investigated and compared. The addition of both HCl and TCA to oxygen produces higher growth rates and improved electrical characteristics. It is shown that the oxidation rate for TCA/O₂ is approximately 30%–40% higher than for HCl/O₂ and that comparable electrical properties can be readily obtained. A TCA/O₂ ratio of 1 mol% gives the optimum process for VLSI applications, though 3 mol% HCl/O₂ gives comparable results. It is suggested that the overall mechanisms governing the processes are similar. However, the TCA process is a safer and cleaner alternative because it generates HCl in situ in the oxidation chamber.     

(Al2O3)f/Al复合材料疲劳损伤模式的SEM研究

通过扫描电子显微镜(SEM)对(Al2O3)f／Al复合材料的疲劳断口和纵截面组织结构进行了观察，研究了复合材料的疲劳损伤模式。研究结果表明：该复合材料兼有钛基和树脂基纤维复合材料疲劳损伤的特点，高应力下由单个裂纹的起源和生长导致复合材料的失效；低应力下，疲劳损伤模式包括纤维劈裂、众多基体裂纹和单个基体裂纹的横向扩展，其中纤维劈裂是主控机制。其更高的疲劳极限可归因于低应力下纤维的纵向劈裂。     

Electrical characteristics and inhomogeneous barrier analysis of Au-Be/p-InSe:Cd Schottky barrier diodes

We have identically prepared Au-Be/p-InSe:Cd Schottky barrier diodes (SBDs) (21 dots) on the InSe:Cd substrate. The electrical analysis of Au-Be/p-InSe:Cd structure has been investigated by means of current-voltage (I-V), capacitance-voltage (C-V) and capacitance-frequency (C-f) measurements at 296 K temperature in dark conditions. The effective barrier heights and ideality factors of identically fabricated Au-Be/p-InSe:Cd SBDs have been calculated from their experimental forward bias current-voltage (I-V) characteristics by applying a thermionic emission theory. The BH values obtained from the I-V characteristics have varied between 0.74 eV and 0.82 eV with values of ideality factors ranging between 1.49 and 1.11 for the Au-Be/p-InSe:Cd SBDs. It has been determined a lateral homogeneous barrier height value of approximately 0.82 eV for these structures from the experimental linear relationship between barrier heights and ideality factors. The Schottky barrier height (SBH) value has been obtained from the reverse-bias C-V characteristics of Au-Be/p-InSe:Cd SBD for only one diode. At high currents in the forward direction, the series resistance effect has been observed. The value of series resistance has been determined from I-V measurements using Cheung’s and Norde’s methods.     

Temperature dependent dielectric studies of Ni/n-GaP Schottky diodes by capacitance and conductance measurements

The dielectric properties of Ni/n-GaP Schottky diode were investigated in the temperature range 140–300 K by capacitance–voltage (C–V) and conductance–voltage (G/ω–V) measurements. The effect of temperature on series resistance (R_s) and interface state density (N_ss) were investigated. The dependency of dielectric constant (ε′), dielectric loss (ε′′), loss tangent (tan δ), ac conductivity (σ_ac), real (M′) and imaginary (M′′) parts of the electric modulus over temperature were evaluated and analyzed at 1 MHz frequency. The temperature dependent characteristics of ε′ and ε′′ reveal the contribution of various polarization effects, which increases with temperature. The Arrhenius plot of σ_ac shows two activation energies revealing the presence of two distinct trap states in the chosen temperature range. Moreover, the capacitance–frequency (C–f) measurement over 1 kHz to 1 MHz was carried out to study the effect of localized interface states.     

1 Volt organic transistors with mixed self-assembled monolayer/Al2O3 gate dielectrics

Control of the threshold voltage and the subthreshold swing is critical for low voltage transistor operation. In this contribution, organic field-effect transistors (OFETs) operating at 1 V using ultra-thin (∼4 nm), self-assembled monolayer (SAM) modified aluminium oxide layers as the gate dielectric are demonstrated. A solution-processed donor–acceptor semiconducting polymer poly(3,6-di(2-thien-5-yl)-2,5-di(2-octyldodecyl)-pyrrolo[3,4-c]pyrrole-1,4-dione)thieno[3,2-b]thiophene) (PDPP2TTT) is used as the active layer. It is shown that the threshold voltage of the fabricated transistors can be simply tuned by carefully controlling the composition of the applied SAM. The optimised OFETs display threshold voltages around 0 V, low subthreshold slopes (150 ± 5 mV/dec), operate with negligible hysteresis and show average saturated field-effect mobilities in excess of 0.1 cm²/V s at 1 V.     

The analysis of the electrical characteristics and interface state densities of Re/n-type Si Schottky barrier diodes at room temperature

The main electrical characteristics of current-voltage (I-V) and capacitance-voltage (C-V) measurements at room temperature of the Re/n-type Si Schottky barrier diodes prepared by pulsed laser deposition (PLD) method have been examined. The values of the basic electrical properties such as forward saturation current (I_o), ideality factors (n), barrier heights (Ф_bo), rectification ratio (RR) and series resistances (R_S) were obtained from I-V and C-V measurements using different calculation methods. At low voltages (V ≤ 0.3 V), the electrical conduction was formed to take place by thermionic emission, whereas at high voltages (V > 0.3 V), a space charge limited conduction mechanism was shown. Furthermore, the interface state densities (N_SS) as a function of energy distribution (E_SS- E_V) was obtained from the I-V data by taking into account the bias dependence of the effective barrier height (Φ_b) for the Re/n-type Si Schottky barrier diodes.     

Electrical and interfacial properties of Au/P3HT:PCBM/n-Si Schottky barrier diodes at room temperature

In this study, a gold/poly(3-hexylthiophene):[6,6]-phenyl C61 butyric acid methyl ester/n-type silicon (Au/P3HT:PCBM/n-Si) metal-polymer-semiconductor (MPS) Schottky barrier diode (SBD) was fabricated. To accomplish this, a spin-coating system and a thermal evaporation were used for preparation of a P3HT/PCBM layer system and for deposition of metal contacts, respectively. The forward- and reverse-bias current–voltage (I–V) characteristics of the MPS SBD at room temperature were studied to investigate its main electrical parameters such as ideality factor (n), barrier height (Φ_B), series resistance (R_s), shunt resistance (R_sh), and density of interface states (N_ss). The I–V characteristics have nonlinear behavior due to the effect of R_s, resulting in an n value (3.09) larger than unity. Additionally, it was found that n, Φ_B, R_s, R_sh, and N_ss have strong correlation with the applied bias. All results suggest that the P3HT/PCBM interfacial organic layer affects the Au/P3HT:PCBM/n-Si MPS SBD, and that R_s and N_ss are the main electrical parameters that affect the Au/P3HT:PCBM/n-Si MPS SBD. Furthermore, a lower N_ss compared with that of other types of MPS SBDs in the literature was achieved by using the P3HT/PCBM layer. This lowering shows that high-quality electronic and optoelectronic devices may be fabricated by using the Au/P3HT:PCBM/n-Si MPS SBD.     

Highly-impermeable Al2O3/HfO2 moisture barrier films grown by low-temperature plasma-enhanced atomic layer deposition

Polymer substrates are essential components of flexible electronic applications such as OTFTs, OPVs, and OLEDs. However, high water vapor permeability of polymer films can significantly reduce the lifetime of flexible electronic devices. In this study, we examined the water vapor permeation barrier properties of Al₂O₃/HfO₂ mixed oxide films on polymer substrates. Al₂O₃/HfO₂ films deposited by plasma-enhanced atomic layer deposition were transparent, chemically stable in water and densely amorphous. At 60 °C and 90% relative humidity (RH) accelerated condition, 50-nm-thick Al₂O₃/HfO₂ had water vapor transmission rate (WVTR) = 1.44 × 10⁻⁴ g m⁻² d⁻¹, whereas single layers of Al₂O₃ had WVTR = 3.26 × 10⁻⁴ g m⁻² d⁻¹ and of HfO₂ had WVTR = 6.75 × 10⁻² g m⁻² d⁻¹. At 25 °C and 40% RH, 50-nm-thick Al₂O₃/HfO₂ film had WVTR = 2.63 × 10⁻⁶ g m⁻² d⁻¹, which is comparable to WVTR of conventional glass encapsulation.     

Temperature dependent current–voltage (I–V) characteristics of Au/n-Si (1 1 1) Schottky barrier diodes with PVA(Ni,Zn-doped) interfacial layer

Current–voltage (I–V) characteristics of Au/PVA/n-Si (1 1 1) Schottky barrier diodes (SBDs) have been investigated in the temperature range 80–400 K. Here, polyvinyl alcohol (PVA) has been used as interfacial layer between metal and semiconductor layers. The zero-bias barrier height (Φ_B0) and ideality factor (n) determined from the forward bias I–V characteristics were found strongly dependent on temperature. The forward bias semi-logarithmic I–V curves for different temperatures have an almost common cross-point at a certain bias voltage. The values of Φ_B0 increase with the increasing temperature whereas those of n decrease. Therefore, we have attempted to draw Φ_B0 vs. q/2kT plot in order to obtain evidence of a Gaussian distribution (GD) of the barrier heights (BHs). The mean value of BH and standard deviation (σ₀) were found to be 0.974 eV and 0.101 V from this plot, respectively. Thus, the slope and intercept of modified vs. q/kT plot give the values of and Richardson constant (A^?) as 0.966 eV and 118.75 A/cm²K², respectively, without using the temperature coefficient of the BH. This value of A^* 118.75 A/cm²K² is very close to the theoretical value of 120 A/cm²K² for n-type Si. Hence, it has been concluded that the temperature dependence of the forward I–V characteristics of Au/PVA/n-Si (1 1 1) SBDs can be successfully explained on the basis of the Thermionic Emission (TE) theory with a GD of the BHs at Au/n-Si interface.     

Improved barrier and mechanical properties of Al2O3/acrylic laminates using rugged fluorocarbon layers for flexible encapsulation

Thin film encapsulation (TFE) with high barrier performance and mechanical reliability is essential and challenging for flexible organic light-emitting diodes (OLEDs). In this work, SF₆ plasma treatments were introduced for surface modifications of acrylic in Al₂O₃/acrylic laminates fabricated by atomic layer deposition (ALD) and ink-jet printing (IJP). It was found that micro-/nano-structures and surface fluoridation appeared on the surface of acrylic, and could be modulated by the discharge power and irradiation of plasma treatment. The water vapor transmission rates (WVTR) of Al₂O₃/acrylic multi-layers decreased evidently because of reducing surface polarity and strong cross-link of acrylic after plasma treatments. Furthermore, the rugged surface and relieved residual stress resulted from etching and heating of acrylic could enhance the mechanical property remarkably. The plasma treated Al₂O₃/acrylic multi-layers with only 3 dyads exhibited a low WVTR value of 1.02 × 10⁻⁶ g/m²/day and more stable mechanical property under 200 iterations blending test by comparative measurements, proving that the introduction of SF₆ plasma surface modifications could improve simultaneously the barrier performance and mechanical reliability prominently of the inorganic/organic multi-layers with no need of extra neutral axis design.     

On the temperature dependence of series resistance and interface states in Al/SiO2/p-Si (MIS) Schottky diodes

The capacitance-voltage-temperature (C-V-T) and conductance-voltage-temperature (G/w-V-T) characteristics of metal-semiconductor (Al/p-Si) Schottky diodes with thermal growth interfacial layer were investigated by considering series resistance effect in the wide temperature range (80-400 K). It is found that in the presence of series resistance, the forward bias C-V plots exhibit a peak, and experimentally shows that the peak positions shift towards higher positive voltages with increasing temperature, and the peak value of the capacitance has a maximum at 80 K. The C-V and (G/w-V) characteristics confirm that the N_ss and R_s of the diode are important parameters that strongly influence the electric parameters in (Al/SiO₂/p-Si) MIS Schottky diodes. The crossing of the G/w-V curves appears as an abnormality when seen with respect to the conventional behaviour of the ideal MS or MIS Schottky diode. It is thought that the presence of a series resistance keeps this intersection hidden and unobservable in homogeneous Schottky diodes, but it appears in the case of inhomogeneous Schottky diode. In addition, the high frequency (C_m) and conductance (G_m/w) values measured under both reverse and forward bias were corrected for the effect of series resistance to obtain the real diode capacitance.     

Temperature and frequency dependent electrical and dielectric properties of Al/SiO2/p-Si (MOS) structure

The electrical and dielectric properties of Al/SiO₂/p-Si (MOS) structures were studied in the frequency range 10 kHz-10 MHz and in the temperature range 295-400 K. The interfacial oxide layer thickness of 320 Å between metal and semiconductor was calculated from the measurement of the oxide capacitance in the strong accumulation region. The frequency and temperature dependence of dielectric constant (ε′), dielectric loss (ε″), dielectric loss tangent (tan δ) and the ac electrical conductivity (σ_ac) are studied for Al/SiO₂/p-Si (MOS) structure. The electrical and dielectric properties of MOS structure were calculated from C-V and G-V measurements. Experimental results show that the ε′ and ε″ are found to decrease with increasing frequency while σ_ac is increased, and ε′, ε″, tan δ and σ_ac increase with increasing temperature. The values of ε′, ε″ and tan δ at 100 kHz were found to be 2.76, 0.17 and 0.06, respectively. The interfacial polarization can be more easily occurred at low frequencies, and the number of interface state density between Si/SiO₂ interface, consequently, contributes to the improvement of dielectric properties of Al/SiO₂/p-Si (MOS) structure. Also, the effects of interface state density (N_ss) and series resistance (R_s) of the sample on C-V characteristics are investigated. It was found that both capacitance C and conductance G were quite sensitive to temperature and frequency at relatively high temperatures and low frequencies, and the N_ss and R_s decreased with increasing temperature. This is behavior attributed to the thermal restructuring and reordering of the interface. The C-V and G/ω-V characteristics confirmed that the N_ss, R_s and thickness of insulator layer (δ) are important parameters that strongly influence both the electrical and dielectric parameters and conductivity in MOS structures.     

Ni3Al/聚酯复合材料的制备及电磁特性研究

采用高能球磨结合热处理工艺合成的金属间化合物Ni3Al粉体,与不饱和聚酯复合制备了Ni3Al/聚酯复合材料,应用微波网络S参数法测量了Ni3Al/聚酯生物复合材料的复介电常数、复磁导率及反射率等电磁性能,结果表明:Ni3Al/聚酯复合材料,在一定频率范围内具有良好的吸波性能,在1~3.25 GHz范围内其反射衰减率均小于–10 dB,该复合材料在民用电磁防护方面具有很好的应用前景。     

Preparation and electrical properties in epoxy resin/In2O3:Sn nanocomposites materials for optoelectronics

To characterize the electrical properties of epoxy resin filled with different contents of Indium Tin Oxides (ITO) nanoparticles (In₂O₃ doped with 15% Sn). We study and discuss the Polarization and Depolarization Current tests (PDC). Using the depolarization current obtained at room temperature under several applied electric field, we perform the time to frequency domain transformation. Our results indicate that the transient currents behavior of the epoxy resin is affected by the presence of ITO nanoparticles. The obtained data were first analyzed in terms of the dielectric permittivity and then transformed to electric modulus to highlight conduction process. In the low frequency region, a weak MWS effect is recorded. This relaxation is ascribed to polarization phenomena taking place at the interfaces between the nano-ITO and the epoxy matrix.     

The source of negative capacitance and anomalous peak in the forward bias capacitance-voltage in Cr/p-si Schottky barrier diodes (SBDs)

The frequency and voltage dependence of capacitance–voltage (C–V) and conductance-voltage (G/ω−V) characteristics of the Cr/p-Si metal semiconductor (MS) Schottky barrier diodes (SBDs) were investigated in the frequency and applied bias voltage ranges of 10 kHz to 5 MHz and (−4 V)−(+4 V), respectively, at room temperature. The effects of series resistance (R_s) and density distribution of interface states (N_ss), both on C–V and G/ω−V characteristics were examined in detail. It was found that capacitance and conductance, both, are strong functions of frequency and applied bias voltage. In addition, both a strong negative capacitance (NC) and an anomalous peak behavior were observed in the forward bias C–V plots for each frequency. Contrary to the behavior of capacitance, conductance increased with the increasing applied bias voltage and there happened a rapid increase in conductance in the accumulation region for each frequency. The extra-large NC in SBD is a result of the existence of R_s, N_ss and interfacial layer (native or deposited). In addition, to explain the NC behavior in the forward bias region, we drew the C–I and G/ω−I plots for various frequencies at the same bias voltage. The values of C decrease with increasing frequency at forward bias voltages and this decrease in the NC corresponds to an increase in conductance. The values of N_ss were obtained using a Hill–Coleman method for each frequency and it exhibited a peak behavior at about 30 kHz. The voltage dependent profile of R_s was also obtained using a Nicollian and Brews methods.     

Effect of dipole location on profile properties of symmetric surface plasmon polariton mode in Au/Al2O3/Au waveguide

This study uses a dipole embedded in Al2O3 layer to excite a symmetric surface plasmon polariton (SPP) mode in Au/Al2O3/Au waveguide to investigate its profile properties by using finite-difference tim...     

中频溅射技术沉积镱铒共掺Al2O3薄膜光致发光

用中频孪生靶溅射法在硅片上制备了镱铒共掺氧化铝薄膜(2 cm×2 cm),在室温下检测到薄膜的位于1 535 nm的很强的光致发光光谱(PL),讨论了泵浦功率、镱铒共掺比例、退火温度对光致发光光谱强度的影响.扫描电镜(SEM)观察分析表明,中频孪生靶溅射法沉积的薄膜致密、均匀、光学缺陷少.实验结果表明镱铒共掺薄膜的荧光强度不随泵浦功率的增加而饱和,最佳的镱铒共掺杂比例9∶1,最佳退火温度850 ℃,对各种实验结果给出了理论的解释.     

新型无铅压电陶瓷NBT-NBSN的研究

采用传统陶瓷制备方法,制备出一种钙钛矿结构无铅新压电陶瓷材料(1-x)(Na1/2Bi1/2)TiO3-x(Na1/2Bi1/2)(Sb1/2Nb1/2)O3(x=0~1.4%,摩尔分数)。研究了(Na1/2Bi1/2)TiO3(NBT)陶瓷B位复合离子(Sb1/2Nb1/2)4 取代对介电和压电性能的影响。X-射线衍射分析表明,所研究的组成均能形成纯钙钛矿(ABO3)型固溶体。陶瓷材料的介电常数-温度曲线显示陶瓷在升温过程中存在两个介电常数温度峰,不同频率下陶瓷材料的介电常数-温度曲线显示该体系材料具有明显的弛豫铁电体特征。检测了不同组成陶瓷的压电性能,发现材料的压电常数d33、厚度机电耦合系数kt和介电常数rε随着x值的增加先增加后降低,在x=0.8%时,陶瓷的d33=97 pC/N,kt=0.50,为所研究组成中的最大值,介电损耗tanδ则随x值的增加而增加。