and then in HCl (37 wt.%) solution for more than 48 h to remove amorphous carbon and catalyst particles. After rinsing by deionized water several times, the puri- fied CNT films were expanded on water surface to form ultrathin films with a thickness of about 50 to 200 nm by adding a few drops of ethanol . Figure 1a illus- trates the fabrication process of CNT/Sithin-film solar cells. First, mono-crystalline Sithin films were prepared by chemical etching of n-type (100) Si wafers (4 in., 2 to 4 Ω cm, 400 ± 5 μm in thickness) in a 50 wt.% KOH so- lution at 80°C to 95°C according to a recent report . The etched Sithin films were rinsed in deionized water several times to remove the residual KOH. Then, an in- sulating tape (approximately 150 μm in thickness) with a circular window of 6 mm in diameter is stuck on one side of the Sithinfilm. The tape can separate the front electrode from the Sithinfilm, protect the Sithinfilm from breaking, and ensure that light illustrates only on the CNT/Si heterojunction. A layer of Ti/Au thinfilm was then deposited on the other side of the Sithinfilm. A piece of purified CNT film was then transferred to the Sithinfilm on the side with tape. Finally, two silver wires were connected to the CNT film and Ti/Au film through silver paint, acting as front and back electrodes, respectively. To improve the efficiency of the solar cells, a few drops of 1 M HNO 3 solution was added on the
Nitrogen-free and nitrogen-doped Zr-Ni-Al-Sithinfilm metallic glasses (TFMGs) were prepared through a plasma emission monitoring (PEM) control process in a co-sputtering system. The corrosion behaviors of these TFMGs coated onto AISI 420 stainless steel substrates in 3.5 wt. % aqueous sodium chloride were studied using electrochemical impedance spectroscopy and equivalent circuit simulation. Nitrogen contents of 11.1 and 15.4 at. % were obtained for TFMGs fabricated under 30 and 70% Zr target poisoning rates, respectively. The amorphous and nitrogen-free TFMG provided the highest corrosion impedance after one hour of immersion in 3.5 wt.% aqueous sodium chloride due to its featureless and dense microstructure. However, the corrosion impedance values of this nitrogen-free TFMG decreased rapidly after immersion for 12 and 24 hours, which could be attributed to its poor adhesion to the AISI 420 stainless steel substrate. Meanwhile, the 15.4 at. % N-doped TFMG showed a stable and good corrosion resistance after immersion for 1 to 24 hours due to its dense nanocomposite microstructure consisting of ZrN nanograins embedded in an amorphous matrix. The lowest corrosion impedance values were found for the TFMG containing 11.1 at. % nitrogen, and this finding can be attributed to the columnar microstructure of this TFMG, which provides a shortcut for the corrosive electrolyte to penetrate through the boundaries to the AISI 420 stainless steel substrate.
and relatively small cracks were generated in the pat- terned electrode. Unfortunately, these results indicate that the volume change of Si was completely not rever- sible during the repeated cycling. Therefore, it is con- cluded that the space between tiles in the patterned Si electrode buffers the volume change of Si during the charge-discharge process and partially disperses the stress generated in the Si electrode. In the next work, it is expected that electrochemical properties of the pat- terned electrode fabricated on a substrate without an oxide layer will be highly improved because the adhe- sion between a film and a substrate will be enhanced by the surface treatment of the substrate. Because of this, the study on a surface-etched substrate is in progress.
reaction rate of the Au atoms into the Si substrate both increase with increasing annealing temperature. This phe- nomenon is conﬁrmed by an inspection of the indentation zone compositions presented in Table 1 for annealing temperatures of 523 K and 623 K, respectively. The ﬁnal phase of the specimens annealed at 523 K and 623 K, respectively, is always amorphous and is the result of a solid-state diﬀusion reaction under isothermal conditions, as reported by Schwarz and Johnson. 18) Although amorphiza- tion during heating occurs as a result of a distortion-induced disorder mechanism, annealing at a temperature of 623 K enables a greater number of Au atoms to diﬀuse into the Si substrate and results in the formation of a more uniform Au/ Cr/Si alloy. However, following annealing at a higher temperature of 723 K, the microstructure of the indented zone is characterized by both amorphous phase and a rod-like eutectic structure, which indicates that a higher annealing temperature is instrumental in generating structural inhomo- geneities. Overall, the present results indicate that nano- indentation to a depth of 1000 nm followed by annealing at a temperature of 623 K represents the optimum process for the fabrication of IC devices and MEMS packages.
the interface bonding property between Al and Cu foil, and also increase the vertical conductivity. Thus, this paper not only investigates the charge-discharge characteristic of Al-Si negative electrodes, but also studies the eﬀects of pre-sputtered Al ﬁlm and the annealed behavior, so as to further understand the potential of the cycling life at high temperature (55 C) for use as a thin ﬁlm negative electrode
process using a quartz-crystal microbalance and was veriﬁed via X-ray reﬂectometry once the deposition process was complete. The nanoindentation tests were performed at room temperature using an MTS Nano Indenter-XP system with a Berkovich diamond pyramid tip. The specimens were indented to a maximum depth of 800 nm using the indenter system set in a depth-control mode. The indentation procedure involved the following steps: (1) loading to the position of maximum load (corresponding to the maximum indentation depth), (2) holding in this position for 10 s, and (3) smoothly unloading over a period of 30 s. The hardness and Young’s modulus of the Ni/Sithin ﬁlm were then calculated from the load-displacement data using the Oliver and Pharr method. 22)
result, accurate methods are required for their character- isation. The hardness and Young’s modulus properties of thin-ﬁlm systems are commonly evaluated using a nano- indentation technique, in which an indenter is driven to a pre- determined depth within the system, held at this depth for a given period of time, and then withdrawn at a steady rate. 6,7) The loading curve obtained during the nanoindentation process often exhibits a discontinuity referred to as a ‘‘pop- in’’ event, 8) while the unloading curve sometimes contains a
(high efficiency and long-term stability) may be used in many ways given the advantages of thinfilm technology (large surface areas area, cheap deposition techniques, economical use of semiconductor materials). To reduce costs, Sithinfilm solar cells on inexpensive foreign substrates have been studied [1-7]. The different methods of growing poly-Sithin films on foreign substrates should aim at large- area grains; such methods include liquid-phase epitaxy (LPE), chemical vapor deposition (CVD) and physical vapor deposition (PVD). These methods enable the fabrication of films with grains (up to ∼100 μm) larger than thinfilm thickness , . When some researchers deposited Sithin films onto substrate-coated seed layers with LPE, uniform and continuous Sithin films with large grains were obtained , [9-12]. For Sithinfilm solar cell applications, the current study investigates the fabrication of Sithin films with different thicknesses on Ag-Al alloy back contact-coated flexible foreign substrates .We investigate the crystallization at various thicknesses to determine the optimized process thickness of poly-Si. The influence of thickness on crystallization is reported. The microstructural and electrical properties of poly-Sithin films on PET fabricated by screen printing are investigated. Important factors are suggested for fabricating uniform poly-Sithin films on foreign substrates.
Figure 4 (a) shows the PL spectrum of ZnO films fabricated at 400°C using GaN buffer layer, and Figure 4 (b) shows the PL spectra of ZnO/Sithinfilm grown at 400°C. Figure 4 shows three main emission peaks. One intense peak centered at 373 nm is near-band emission, which corresponds to the exciton emission from near conduction band to valence band. Another weak one located at 456 nm is defect emission. As shown in Figure 4, merely the weak defect emission band centered at 456 and 485 nm can be observed in two thin films. This blue emission located at 456 nm most likely derives from electronic transition from the donor level of Zn interstitial to acceptor energy level of Zn vacancy according to Sun's calculation by full-potential linear muffin-tin orbital method [25-27]. This shows that some Zn i atoms exist in fabricated ZnO thin films. The
Figure 6 illustrates post-cycling SEM images of the samples. The post-cycling investigations of the flat Si anode (Figure 6a) revealed the extensive delamination of the Sithinfilm from the flat substrate with the remaining Si islands being around 15 mm in length. One can see that the islands’ edges do not touch the substrate, indicating electrical contact loss. From the SEM images of the second anode (Figure 6b), we detected that the sputtered Sithinfilm experiences cracking, forming is- lands with approximately the same dimensions as those for Si on the flat substrate. However, the distances between islands are around few micrometers and the edges of the islands were Figure 4. Electrochemical test results. a) CV for Sithinfilm at a scan rate of
cells exhibited low reflectance of <5 % over a broad range 300 nm < λ < 1050 nm for nanowire length greater than 1 μm . The results are interesting given that the dimensions of the MCEE SiNWs commonly etched using AgNO3/HF solution, with diameters from 30– 150 nm and spacing of 20–80 nm , are not in the op- timized range for effective scattering of the main solar spectrum. This leads to the question of the origin of their strong light trapping properties. Recently, interest in the effect of disorders on the optical performance of Si nanostructures has grown [17–20]. Some theoretical studies have been done on the SiNW arrays without any underlying Sithinfilm using the finite-difference time- domain (FDTD) method [17, 18] and transfer matrix method (TMM) . In these studies, individual struc- tural parameters of the SiNW arrays such as diameter , position [17–19], and length  have been varied one at a time to study their effects on the optical proper- ties of the SiNW arrays. The results have shown that the disorders in the SiNW arrays resulted in improved light absorption as compared to the periodic structure with comparable dimensions, attributed to the presence of additional resonance modes and broadening of the exist- ing modes [17–19]. In this work, we have carried out optical simulations based on a hybrid structure of ran- dom SiNW arrays on an underlying Sithinfilm, and with PEDOT:PSS on top using the finite element method (FEM) . We investigate the effects of the random- ness of the MCEE SiNW arrays, in terms of their diam- eter and spacing, on the optical properties of the hybrid SiNW/PEDOT:PSS solar cells. Instead of varying the pa- rameters randomly one at a time over a pre-defined range, we allow both the SiNW diameter and spacing to
about 3–4 . When the crystalline ab-plane is inclined from the sample surface, the surface-normal direction will be defined with contributions from both the crystallo- graphic c-axis and the a- (or b-) axis even though the lat- ter will have a minor contribution. Then the photocarriers generated at the surface, which otherwise are accelerated simply along the surface-normal direction, will experience an anisotropic electrostatic potential or anisotropic trans- port behavior as they travel inside of the film. Conse- quently, THz light emitted through a surge current can have the finite anisotropic response on the sample azi- muth. Since x-ray diffraction results revealed the relative tilting angle between diffraction planes of the TI film and the substrate, crystallographic planes can be drawn differ- ently as in Fig. 3b where the crystal plane of the substrate is inclined with respect to the sample surface and the TI crystal plane is in parallel with the sample surface. We consider that the configuration in Fig. 3a instead of that in Fig. 3b is more preferable to explain the anisotropic THz emission results since the THz emission in the case of Fig. 3b should appear isotopically as a function of Φ. Al- though the anisotropic THz responses in the variation of Φ were discussed in terms of the surge current THz emis- sion process, it should be noted that the results would be explained also by the optical rectification process by con- sidering the lowered surface symmetry.
examined the eﬀects of the compositions of two metals, Pd and Cu, on thermal properties. In order to eliminate the eﬀect of Si content, the sample group having almost the same Si content (Si = ca. 15 at%) and diﬀerent Pd/Cu atomic ratios were selected. Their DSC charts are shown in Fig. 6. This ﬁgure shows that T g tends to increase when Pd/Cu ratio is
domains are formed during the Ni cooling process. These twins and rotated domains allow for more favorable slip systems within the crystal and thus more relaxation within the Ni film. To confirm this, the different slip systems of the Ni crystal must be considered as well as the critical resolve stress of the system under directional stress. The smaller the misfit strain in a system, the harder it is for that strain to be relaxed. With high values of strain, the critical thickness of a film, in which dislocations will form at the free surface, is a few monolayers or less allowing dislocations to easily move to the film substrate interface and relax the film. However, as the strain decreases, the critical thickness of the film increases. In order for dislocations to glide to the interface, the critical resolve shear stress (𝜏 𝑟 ) in the
The 2D ATLAS simulation structure consists of 11 periods of alternating intrinsic well and heavily doped barrier layers; and the simulated p-type Si/SiGe/Si QW structure is illustrated in figure 14(a). The total film stack thickness depends on the combined width of well and barrier. Both thermal and electrical contacts (illustrated by the grey bars) are placed simultaneously at the vertical ends of the structure so that both heat and electrical current flow parallel (x direction) to the superlattice layers. A thermal condition of 10K temperature gradient is maintained across 3µm-long film stacks. However, a practical TE element can be several centimeters long with hundreds of Kelvin temperature difference.
can overcome the issue of highly resistive nature of the traditional Si-based dielectric matrix materials, and 10 4 times improvement of ρ is obtained. The ρ largely increases for the sample annealed at 800°C, which may have resulted from the excess film prominences produced during annealing since the film prominences will lead to local broken circuit regions at the interface of film/substrate and significantly increase the resistivity. Hence, we can con- clude that annealing at 700°C is a more suitable annealing condition to have better crystallization of Si QDs in the crystalline ZnO matrix, low ρ, and high transmittance in the long-λ range. The logarithmic I-V curve of the sample annealed at 700°C is shown in Figure 5b, and its inset shows the corresponding linear I-V curve in magnification. It clearly exhibits not only a good rectification ratio of 3.4 × 10 3 at ±5 V but also a low turn-on voltage (V t ) of
In this work, PLMA thinfilm doped with Mn:ZnSe QDs was spin-deposited on the front surface of Si solar cell in order to improve the solar cell efficiency via PL conver- sion. Significant efficiency enhancements (approximately 5% to 10%) were achieved indeed under AM0 condi- tions. Both the effects of AR and PL conversion contrib- uted to the solar cell efficiency enhancements but that of PL took a small portion. A precise assessment of PL contribution to the efficiency enhancement was made by investigating the PV responses of Si solar cells coated with QD-doped PLMA to monochromatic and AM0 light sources as functions of QD concentration, com- bined with reflectance and EQE measurements. Our work shows that the real PL contribution might not be all that as reflected by the apparent efficiency enhance- ment, and cautions are to be taken when applying the
Using the RIGAKU D/MAX-2200 type PC X-ray diffraction of the phase of the sample were measured for the Cu target radiation. λ = 0.15418 nm, the working voltage of 40 kV, current of 30 mA, the scanning range of 10 ˚ - 80˚, the scanning speed was 20/min. As can be seen from the Figure 2, doping ions easily lead redox reac- tion in the titania lattice surface, then produced oxygen vacancy or interstitial titanium by diffusion, thereby in- hibiting the interaction between different titanium atoms, transition hinder anatase to rutile phase, to improve the light absorption ability of TiO 2 thin films.
and Mn on properties of polythiophene thinfilm was then studied. The synthesized polythiophene were characterised by electrochemica technigues.Fourier transform infrared spectroscopy (FTIR), SEM analysis and XRD analysis. Chemical composition of polythiophene film was investigated by FTIR spectroscopy. Surface morphology was influence by dopant ,SEM analysis of PTh/TiO 2 image seems to be uniform microporous on the