Effect of Thickness and Buffer Layer on Magnetization and Spin Dynamics of Ferromagnetic Heterostructure: Microwave Monolithic Device Functionality

Effect of buffer layer and film thickness on the growth mechanism of La0.67Ca0.33MnO3 films

Bi0.9Gd0.1Fe0.9Co0.1O3 (BGFC) films were deposited successfully on Pt(111)/Ti/SiO2/Si(100) and SrRuO3 (SRO)/Pt(111)/Ti/SiO2/Si(100) substrates by radio frequency magnetron sputtering. Effects of sputtering power, buffer layer and film thickness on ferroelectric properties of the sputtered BGFC films were studied. X-ray diffraction demonstrated that all films had a single perovskite-type structure. Highly (012) and (024)-oriented BGFC films were formed on Pt(111)/Ti/SiO2/Si(100) and SRO/Pt(111)/Ti/SiO2/Si(100) substrates. The ferroelectric test indicated that the leakage current density of BGFC films sputtering at 40 W was smaller than that of BGFC films sputtering at 120 W, and its ferroelectric property was better than that of BGFC films sputtering at 120 W. Furthermore, the leakage current density of BGFC film with SRO buffer layer was improved and reduced by one order of magnitude under the same film thickness and sputtering power, comparing with the leakage current density of BGFC film without SRO buffer layer on Pt(111)/Ti/SiO2/Si(100) substrate. The ferroelectric property of BGFC thick film is better than that of BGFC thin film under the same sputtering power and applied electric field. The logJ–logE plots of BGFC films indicated that the leakage mechanisms of BGFC films with sputtering power of 40 and 120 W belong to the space-charge-limited conduction and Ohmic conduction, respectively. The mechanisms of the effects of sputtering power, buffer layer and film thickness on the ferroelectric properties of BGFC films were discussed.

Various low-temperature (LT) ultra-thin buffer layers have been fabricated on the GaAs (001) substrate. The buffer layer is decoupled from the host substrate by introducing low-temperature defects. The 400 nm In0.25Ga0.75As films were grown on these substrates to test the ‘compliant’ effects of the buffer layers. Atomic force microscopy, photoluminescence, double crystal x-ray diffraction and transmission electron microscopy were used to estimate the quality of the In0.25Ga0.75As layer. The measurements indicated that the misfit strains in the epilayer can be accommodated by the LT ultra-thin buffer layer. The strain accommodation effects of the LT defects have been discussed in detail.

ABSTRACTCarbon nanotubes (CNTs), with exceptional thermal and mechanical properties as well as inherently high surface area, are an attractive candidate for integrating into thermal structures of advanced power electronics. Growth of vertically aligned carbon nanotubes (VACNTs) directly onto copper (Cu) substrates is a promising approach to apply CNTs as novel thermal interface materials (TIMs) in electronics packaging. However, compared to growing CNTs on conventional inert substrates such as SiO2, direct growth of controllable CNT arrays onto Cu substrates is significantly more challenging due to the diffusion of metallic catalyst into the substrate during growth. By depositing an appropriate buffer layer on the Cu substrate surface, VACNTs of good alignment and high quality were reproducibly synthesized on the Cu substrate via the chemical vapor deposition (CVD) method in this study. The effect of different buffer layers on the CNT growth, nanotube structure and quality was investigated (SEM, Raman), particularly in terms of the interfacial properties between the CNT array and Cu substrate (Tensile compression force tester, Laser Flash Analysis). Our experimental results indicated that the buffer layer material, deposition method, and thickness play a key role in regulating the CNT layer growth/structure, leading to variable mechanical and thermal properties. The fundamental understanding thus obtained allows the successful synthesis of VACNT on copper substrates with desired structure and properties.

Due to the simultaneously superior optical transmittance and low electrical resistivity, transparent conductive electrodes play a significant role in semiconductor electronics. To enhance the electrical properties of these films, one approach is thickness increment which degrades the optical properties. However, a preferred way to optimize both electrical and optical properties of these layers is to introduce a buffer layer. In this work, the effects of buffer layer and film thickness on the structural, electrical, optical and morphological properties of AZO thin films are investigated. Al-doped zinc oxide (AZO) is prepared at various thicknesses of 100 to 300 nm on the bare and 100 nm-thick indium tin oxide (ITO) coated glass substrates by radio frequency sputtering. Results demonstrate that by introducing ITO as a buffer layer, the average values of sheet resistance and strain within the film are decreased (about 76 and 3.3 times lower than films deposited on bare glasses), respectively. Furthermore, the average transmittance of ITO/AZO bilayer is improved nearly 10% regarding single AZO thin film. This indicates that bilayer thin films show better physical properties rather than conventional monolayer thin films. As the AZO film thickness increases, the interplanar spacing, d(002), strain within the film and compressive stress of the film in the hexagonal lattice, decreases indicating the higher yield of AZO crystal. Moreover, with the growth in film thickness, carrier concentration and optical band gap (Eg) of AZO film are increased from 4.62 × 1019 to 8.21 × 1019 cm−3 and from 3.55 to 3.62 eV, respectively due to the Burstein-Moss (BM) effect. The refractive index of AZO thin film is obtained in the range of 2.24–2.26. With the presence of ITO buffer layer, the AZO thin film exhibits a resistivity as low as 6 × 10−4 Ω cm, a sheet resistance of 15 Ω/sq and a high figure of merit (FOM) of 1.19 × 104 (Ω cm)−1 at a film thickness of 300 nm. As a result, the quality of AZO thin films deposited on ITO buffer layer is found to be superior regarding those grown on a bare glass substrate. This study has been performed over these two substrates because of their significant usage in the organic light emitting diodes and photovoltaic applications as an enhanced carrier injecting electrodes.

The present work dealt with the fatigue and residual stress (RS) effects of a soft buffer layer (BL) between the parent metal and the weld metal (WM) on welded high-strength low-alloy (HSLA) steel. Six strategies were pursued by varying BL thickness and changing U-notch position with respect to the WM in extended-compact tension specimen. The U-notch position was changed to study the effect of welding RS field, acting along the fatigue crack growth path. The welded HSLAs with BLs strategies were compared to the specimens without BLs strategies, before and after releasing RS respectively. The results demonstrated that the incorporation of a thin BL of 4 mm significantly reduced the fatigue crack growth rate (da/dN) when the RS in the welded HSLA was released by machining a U-notch in the WM. A thick BL of 10 mm was found to be beneficial to fatigue resistance when a U-notch was in the PM.

In this study, the magnetic properties of Si(100)/X5/(Co0.3/Ni0.5)3/Y5 (X: Pt, Cu and Y: Pt, Cu, all thicknesses are nm) multilayers were investigated using ferromagnetic resonance technique (FMR). In sample sets all layers (buffer, cap, and Co) were grown by magnetron sputtering while Ni sub-layers were grown by molecular beam epitaxy (MBE) at high vacuum. The effective magnetic anisotropy is 300 mT when copper is used as the buffer and cap layer, 290 mT when the buffer layer is copper, and the cap layer is Pt. On the other hand, it is seen that the effective magnetic anisotropy is 350 mT when Pt is used as buffer and cap layer, and 150 mT when Pt buffer and Cu cap layer are used. Furthermore, magnetic easy axis is out of plane when the Pt buffer layer is used, while the magnetic easy axis is parallel to the plane when the Cu buffer layer is used. The results show that the buffer and cap layers of Co/Ni thin films, which are frequently used in the field of spintronics influence the magnetic properties.

The effect of buffer and cap layer on thermally stable perpendicular magnetic anisotropy (PMA) in buffer/CoFeB/MgO/cap structure was designed to detailed study. Not only the buffer layer is crucial, but the type of cap layer also affects the thermal stability of PMA. Relatively to the Ta samples, the W samples adopting W buffer or cap layer get a wider PMA thickness range for further increasing thermal stability of PMA in magnetic random access memory (MRAM) applications. And the same as the W buffer layer, the annealing temperature for W cap layer is also increased 30°C (from 270°C to 300°C). Via the detailed anomalous Hall effect (AHE) measurements, the thermal stability of PMA in buffer/CoFeB/MgO/cap was investigated. This work provides a promising way to obtain high thermal stability of PMA in CoFeB-MgO-based spintronic applications, and it is significant for designing the next-generation information storage devices.

Effect of Ca and buffer layers on the performance of organic light-emitting diodes based on tris-(8-hydroxyquinoline) aluminum

Effect of buffer layer on the growth of GaN on Si substrate

The pyroelectric thermal detectors were prepared with lead zirconate titanate (PZT) ceramics, where a signal electrode had a structure of Au/metallic buffer/(PZT ceramic). The effect of buffer layer on the voltage responsivity was investigated with a response to step signal, taken by dynamic pyroelectric measurement. Pyroelectric ceramic wafer was prepared by mixed oxide technique. Au layer (thickness: 50 nm) and metallic buffers (thickness: 0 - 20 nm) of Cr, NiCr (80/20), and Ti were prepared by dc magnetron sputtering. In order to improve the light absorptivity, an Au-black was coated on Au signal electrode by thermal evaporation. At steady state, the output voltage (V<SUB>o</SUB>) was decreased with increasing chopping frequency in the range of 1 - 100 Hz. A sensor without buffer showed the severe time-drift and instability in the output signal. However, the sensors with buffer layer showed the stable outputs. For step radiations, rising time (t<SUB>p</SUB>), peak voltage (V<SUB>p</SUB>), and initial slope (k) of the output voltage were dependent upon the thickness and materials of buffer layer. The mechanical and electrical contacts between Au electrode and PZT ceramics were improved by inserting the metallic buffer layer. Considering the characteristics of the output voltage, the optimum thickness of buffer layer was about 15 - 20 nm, and the sensors with Ti buffer of 15 - 20 nm in thickness showed the good detectivity. Therefore, the stability and reliability of the thermal sensors could be improved by use of appropriate buffer layer.

Investigations on the effect of buffer layer on CMTS based thin film solar cell using SCAPS 1-D

Effect of buffer layer on thermochromic performances of VO2 films fabricated by magnetron sputtering

In order to study the influence of the buffer layer on the explosive drive of the reactive fragment, for the reactive fragment warhead of the same structure, the warhead static explosion test and the break-through target test method were used to test the fragment integrity and the fragment integrity of the reactive fragment warhead of the reactive fragment warhead with several different thickness silicone rubber buffer layers. The initial velocity of the fragment was measured, and its integrity and the variation law of the initial velocity were analyzed. The results show that with the increase of the thickness of the buffer layer, the integrity of the reactive fragments increases. When the thickness of the buffer layer is 2 mm, the fragment integrity rate is zero, and when the thickness of the buffer layer is greater than 8 mm, the integrity rate is greater than 0.85. The difference in the initial velocity of the warhead of the same reactive fragment is small, mainly because with the increase of the thickness of the buffer layer, the initial velocity of the fragment decreases mainly because the loading ratio of the warhead decreases; the buffer layer has a significant effect on reducing the initial velocity of the reactive fragment, and k=0.83 can be used The modified Gurney formula was used to estimate the initial velocity of the reactive fragments of the silicone rubber buffer layer.

ABSTRACTWe use micro-Raman and photoluminescence (PL) spectroscopy to study the effects of an a-Si:H buffer layer at the i/p interface of the mixed-phase silicon solar cells. We find that the signature of the crystalline 520 cm−1 mode still appears on the Raman spectrum for the cells with a 100 Å thick a-Si:H buffer layer; but it completely disappears for cells with a 500 Å thick a-Si:H buffer layer. At 80 K, the PL spectral lineshape reflects the features of the electronic states in the band tails. The characteristics of the PL spectra of the mixed-phase cells are a narrower main band than the standard a-Si:H band and an extra low energy band from the grain boundary region. As the thickness of the a-Si:H buffer layer increases, the PL main band becomes broader, and the low energy band is depressed. We find that, after light soaking, the PL main band is slightly broadened for the cells with no a-Si:H buffer layer, almost no change for the cells with a 100 Å thick buffer layer, and a remarkable decrease in total PL intensity for the cells with a 500 Å thick buffer layer. In addition, the PL intensity of the defect band increases after light soaking for the cells with a 500 Å thick buffer layer, where light-induced defect generation in the a-Si:H buffer layer masks the changes in the mixed-phase intrinsic layer. The Raman and PL results are consistent with previous observations of the effect of an a-Si:H buffer layer on the performance and metastability against light soaking for mixed-phase solar cells.