Silicon Wafer Substrates Research Articles

Enhancement of transmission characteristics for the antenna system printed on silicon wafer substrate by using FSS‐based coplanar parallel reflector

Here, a silicon-substrate-based four element antenna system is investigated by using a coplanar frequency selective surface (FSS) as a novel parallel reflector to improve radiation and transmission characteristics of the antennas. The four antennas are arranged around the square FSS, and one of the antennas is used as the transmitting element, while the other three as the receiving ones. It is found that, owing to the stopband filtering and the linearly changing reflection phase of the designed coplanar FSS, the gain and directivity of the transmitting antenna have been greatly improved, and that the antenna system transmission coefficients, including S 21, S 31 and S 41, have been significantly increased. Two types of the antenna systems have been designed and fabricated on a P-type silicon wafer substrate for the cases with and without a coplanar FSS reflector. The measured S-parameters are essentially consistent with those simulated. In comparison with the case without the FSS, the transmission coefficients of S 21, S 31 and S 41 for the system with the FSS have been increased about 6.42, 5.97 and 5.89 dB at the center frequency of 5.42 GHz, respectively. Furthermore, the proposed coplanar FSS exhibits distinct advantage of low-profile compared to the conventional vertical FSS reflector.

Effect of Si/O doping on the thermal stability of non-bonded hydrogenated diamondlike carbon coatings

Diamond-like carbon coatings containing Si and O (a-C:H:SiOx) were deposited onto 316L steel and silicon wafer substrates using a mixture precursor of hexamethyldisiloxane (HMDSO) and acetylene under a high bias voltage. Then, the coated coupons were annealed in an argon media. The hydrogen content in the coating was measured by 2 MeV 4He+ elastic recoil detection analysis (ERDA). The structure and morphology evolution during annealing were characterized by scanning electron microscopy (SEM), mass spectrometry (MS), Fourier transformation infrared spectroscopy (FTIR), Raman spectra, and X-ray photoelectron spectroscopy (XPS). The mechanical properties were investigated using a residual stress tester and nanoindentor. The results showed that under a high bias voltage a large amount of the hydrogen of the a-C:H:SiOx coatings did not bond with carbon. Si and O preferred to form SiC bonds and SiO bonds respectively to enhance C sp3 fraction, relax the residual stress, and depress the graphite cluster growth. During annealing, combining with C sp3 rehybridization, the transformation of the SiC bond to SiO or Si-C-O bonds caused hardness and residual stress variation. The a-C:H:SiOx coatings still held more than 12 GPa hardness after annealing at 590 °C for 4 h, while the hardness was approximately 8 GPa for the pure a-C:H coating.

Preparation and Characterization of Solar Thermal Absorbers by Nanoimprint Lithography and Sputtering

ABSTRACTSelective solar absorbers comprised of plasmonic materials offer great flexibility in design along with a highly promising optical performance. However, the nanopattern generation, typically done with electron beam writing, is a very time-intensive process. In this work, we present a fast, scalable, and flexible method for the fabrication of plasmonic materials by the combination of a deposition mask prepared by nanoimprint lithography and thin film deposition by magnetron sputtering. The fabrication process was first performed on silicon wafer substrates using AFM and SEM measurements to calibrate the deposition time, determine maximal deposition height, and characterize samples. Afterwards, the process was transferred to polished Inconel NiCr-alloy substrates used in high temperature solar absorbers. To investigate the adhesion properties of the nanostructure on the substrate, two different deposition methods were investigated: DC magnetron sputtering and High Power Impulse Magnetron Sputtering (HiPIMS).

Procedure for the Transfer of Polymer Films Onto Porous Substrates with Minimized Defects.

The fabrication of devices containing thin film composite membranes necessitates the transfer of these films onto the surfaces of arbitrary support substrates. Accomplishing this transfer in a highly controlled, mechanized, and reproducible manner can eliminate the creation of macroscale defect structures (e.g., tears, cracks, and wrinkles) within the thin film that compromise device performance and the usable area per sample. Here, we describe a general protocol for the highly controlled and mechanized transfer of a polymeric thin film onto an arbitrary porous support substrate for eventual use as a water filtration membrane device. Specifically, we fabricate a block copolymer (BCP) thin film on top of a sacrificial, water-soluble poly(acrylic acid) (PAA) layer and silicon wafer substrate. We then utilize a custom-designed, 3D-printed transfer tool and drain chamber system to deposit, lift-off, and transfer the BCP thin film onto the center of a porous anodized aluminum oxide (AAO) support disc. The transferred BCP thin film is shown to be consistently placed onto the center of the support surface due to the guidance of the meniscus formed between the water and the 3D-printed plastic drain chamber. We also compare our mechanized transfer-processed thin films to those that have been transferred by hand with the use of tweezers. Optical inspection and image analysis of the transferred thin films from the mechanized process confirm that little-to-no macroscale inhomogeneities or plastic deformations are produced, as compared to the multitude of tears and wrinkles produced from manual transfer by hand. Our results suggest that the proposed strategy for thin film transfer can reduce defects when compared to other methods across many systems and applications.

Uncompensated grain boundary spin driven exchange bias effect in granular NiO film

Significant exchange bias effect has been identified in the granular Nickel oxide (NiO) film prepared by sol-gel dip-coating technique on a silicon wafer substrate. Atomic force microscopy displays grain sizes in the range 15–25 nm. Thermal variation of zero field cooled magnetization (ZFC) measured in 500 Oe shows a broad peak around 156 K. Below 25 K, both field cooled (FC) and ZFC magnetization display a significant rise indicating existence of a ferromagnetic (FM) component, which is suggested due to the uncompensated (UC) spins residing at the grain boundaries. The systematic shift in the magnetic hysteresis loops are observed when the sample is field cooled. The shift is the manifestation of exchange bias effect (EB). Training effect is observed at 6 K which could be analyzed by a recursive formula in the framework of spin configurational relaxation model. We propose that pinning mechanism at the interface between antiferromagnetic core and shell consisting of uncompensated spins leads to the EB effect in the granular NiO film.

Determination of the structural, morphological and optical properties of graphene doped SnO thin films deposited by using thermionic vacuum arc technique

Tin Oxide (SnO) compounds, both SnO and SnO2 are wide band gap semiconductors, which are highly optically transparent in the visible range (400–700 nm). Graphene is also highly optically transparent and durable material. Doped SnO thin films can be defined as transparent conductive oxide (TCO) thin films, similarly to indium tin oxide (ITO), aluminum doped zinc oxide (AZO) and gallium doped zinc oxide (GZO) thin films. In this study, the graphene doped thin films are deposited onto glass and Silicon (Si) wafer substrates by using thermionic vacuum arc (TVA) technique. The structural, morphological and optical properties of graphene doped SnO thin films were investigated by various methods such as X-ray diffraction spectroscopy, atomic force microscopy, field emission scanning electron microscopy, Fourier Transform infrared spectroscopy, Raman spectroscopy, Interferometer, Fluorescence spectrometer and UV–Vis spectrophotometer. According to results, the deposited thin films have high transparency (90%), polycrystalline structure, low roughness and high homogeneity. The thicknesses of the thin films were measured as 10 nm and 8 nm deposited onto glass and Si substrate, respectively. Graphene flakes combining with other graphene flakes and SnO compounds formed diamond poly type structures along with graphene oxide (GO) structures. The band gap values of the thin films were measured as 3.11 eV and 3.33 eV deposited onto glass and Si substrate, respectively. These results show that by doping graphene the band gap value shifted towards to violet region from ultraviolet region.

Oblique angle deposition of nanocolumnar TiZrN films via reactive magnetron co-sputtering technique: The influence of the Zr target powers

Nanocolumnar titanium zirconium nitride (TiZrN) films deposited on silicon wafer substrates were fabricated via reactive magnetron co-sputtering with oblique angle deposition (OAD) at room temperature. The influences of the sputtering power of Zr target varied from 100 to 300 W, on the structure, morphology and composition of the nanocolumnar TiZrN film were investigated by gracing-incidence X-ray diffraction (GIXRD), field emission scanning electron microscope (FE-SEM), transmission electron microscope (TEM), energy dispersive X-ray spectroscopy (EDS), atomic force microscope (AFM) and photoelectron spectroscopy (PES). The GIXRD patterns revealed that the prepared films deposited at different sputtering powers of Zr target were crystalline in cubic phase with preferential orientation (111) and (222) planes of ZrN and TiN, respectively. The morphology obtained from FE-SEM showed well aligned slanted nanocolumnar structure, which come from the OAD technique. Increasing the sputtering power of Zr target, led to high adatom energy and enhanced collision effect during film deposition which the nanocolumnar showed obvious change in the diameter, length and tilt angle. The EDS mapping inside the nanocolumnar confirmed the homogeneity of the Ti, Zr and N element distributed in the nanocolumnar TiZrN films. Finally, the tribology behavior was preliminarily investigated based on the hardness of the nanocolumnar film and discussed in this manuscript.

Synthesis and optimization of low-pressure chemical vapor deposition-silicon nitride coatings deposited from SiHCl3 and NH3

Stoichiometric silicon nitride films were deposited by low-pressure chemical vapor deposition from the SiHCl3-NH3-H2-Ar system in a hot wall reactor at pressures ranging from 0.3 to 2 kPa. The films are amorphous for deposition temperatures up to 1000 °C and crystalline, in the α-form, at 1200 °C and above. A method for evaluating the internal stresses based on the curvature of the silicon substrate wafer and the resulting silicon Raman peak shift was developed. Some amorphous films exhibit high internal tensile stresses that can lead to cracking during deposition depending on the mechanism and effective precursors involved. Residual stresses can thus be reduced and cracking avoided by, in descending order of importance, reducing the concentration of reactive gases through dilution, increasing the deposition temperature and decreasing the total pressure. The effects of these parameters on the intrinsic stresses were related to the amount of residual hydrogen successively incorporated and thermally released during the growth of the coating according to the Noskov's model.

Observations of the initial stages on reactive gas-timing sputtered TaO thin films by dynamic in situ spectroscopic ellipsometery

Dynamic in-situ spectroscopic ellipsometry (iSE) was employed to investigate the growth mechanism of the tantalum oxide (TaO) film on silicon wafer substrate deposited by reactive gas-timing RF magnetron sputtering compared with conventional reactive sputtering. The effect of reactive gas timing parameter on physical structure and optical property were analyzed by both the continuous and island film growth model with Tauc-Lorentz optical model. The variation of refractive index, film thickness and void volume fraction were obtained from dynamic fits of iSE data indicated that the growth process of the amorphous TaO thin films was divided into two regimes: the nucleation stage and continuous-layer stage. These stages were observed during deposition although the initial film growth stage corresponds to the island film growth model. The study demonstrates that sputtered TaO by the RGT technique at the O2 on-off gas timing has played a crucial factor in improving the formation of nucleation stage and that the deposited TaO thin films were high deposition rate with high refractive index. The complementary field emission scanning electron microscope (FE-SEM) and transmission electron microscope (TEM) showed a good agreement with the film thickness and morphology obtained from dynamic iSE measurement. The real-time monitoring of iSE offers important evidences to understand the growth mechanism of reactive gas-timing technique.

Synthesis and Characterization of Plasma-Polymer Gate Dielectric Films for Graphene Field Effect Transistor Devices

In this study, a gate dielectric suitable for application in field effect transistors (FETs) was synthesized. Gate dielectrics were deposited using cyclohexane via plasma-enhanced chemical vapor deposition. These films were synthesized on silicon wafers substrates with plasma powers adjusted from 10 to 60 W. Graphene was synthesized on a nickel substrate by a thermal chemical vapor deposition process and coupled to the plasma-polymer via water transfer. Alpha step, Fourier-transform infrared spectroscopy, Raman spectroscopy, and atomic force microscopy findings in addition to water contact angle measurements were analyzed to characterize the physical and chemical properties of the plasma-polymer thin film. Furthermore, a probe station was used to characterize the FET devices fabricated using such films.

Structure and Oxidation Behavior CrN Thin Films Deposited Using DC Reactive Magnetron Sputtering

The CrN ceramic thin films were deposited using DC reactive magnetron sputtering system on silicon wafer substrate. Oxidation behavior was carried out in air at evaluated temperatures ranging from 500 °C up to 900 °C for 2 h. The structure and element composition of the films at different thermal annealing temperatures ranging were investigated by X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS), respectively. The oxidation activation energies of the films were calculated using Arrhenius equation. The changes in the crystal structure from CrN to Cr2O3 phase were investigated from XRD results. The accumulation of grains on surface was confirmed by FESEM micrographs. The cross-section analysis showed an apparent columnar feature with dense structure for the film annealed at low temperature, and becomes porous when increasing the annealing temperature. The thickness was increased from 1.43 to 2.67 μm. The EDS studies indicated the existence of Cr, N and O with different elements compositions on the deposited thin films. The oxidation activation energy for the CrN thin films is 124.4 kJ/mol.

Rapid synthesis of a highly active and uniform 3-dimensional SERS substrate for on-spot sensing of dopamine.

A rapid method is described for the preparation of a highly uniform and sensitive SERS substrate by an improved 'drop-and-dry' method. Gold nanobipyramids (Au NBPs) were prepared inside the nanoholes (nanowalls) of anodic aluminum oxide (AAO) templates with a typically 5-μm nanohole depth. The SERS substrate can be prepared by this method within 40s and on large scale. The SERS signals obtained with this Au NBPs-AAO substrate is stronger by four-orders of magnitude compared to conventional a silicon wafer substrate. The SERS signal for dopamine (DA; measured at 1311cm-1) is found to be enhanced by a factor of 2.2 × 108. The response to DA extends from 10nM to 0.1mM, and the limit of detection is 6.5nM (at S/N= 3). The assay was applied to the determination of DA in spiked human serum. Graphical abstract Schematic presentation of a highly active and uniform 3-dimensional substrate composed of gold nanobipyramids and anodic aluminum oxide (Au NBP/AAO). It was used for on-spot sensing of dopamine.

Physical and Chemical Morphology of Passively Sampled Environmental Films

This work presents spatially resolved physical and chemical surface characterization of passively sampled environmental films developed in urban, suburban, and metropolitan locations. Environmental surface films are important mediators of atmospheric particulate matter (PM) and persistent organic pollutants (POPs) fate and transport. The films are developed via dry deposition onto silicon wafer substrates for time scales ranging from 1 to 52 weeks. Spatial and chemical morphologies of the films are analyzed by bright-field, scanning electron, and atomic force microscopies. Surface feature sizes span 6 orders of magnitude, from the millimeter to nanometer regimes, indicative of super- and sub-micrometer PM as well as conformal films of nanoscale PM and semivolatile molecules. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) imaging data are analyzed to report the films’ chemical morphology and speciation which include a range of organic and inorganic species. Increases in surface coverages (ca. 5%...

Effect of light induced heat treatment on the structural and morphological properties of Linbo3 thin films

In this research, the spin coating technique has been used to achieve the deposition process of the lithium-niobate. A halogen lamp has used to maintain required heating during the deposition process. A Range of temperatures (60 - 120 °C) was applied on a substrate of a single crystal silicon wafer to maintain high quality deposition process. The deposited films were subsequently annealed to annealing temperature of 500 °C. Films were characterized and analyzed using X-ray diffraction (XRD), atomic force microscopy (AFM), and scanning electron microscope (SEM), Raman spectroscopy. The results showed there is a significant impact that the substrate temperature can role over the structural and morphological properties of the prepared films. It also showed that there is a critical value of substrate temperature yields to the best combination of morphological and structural properties. Moreover, the higher values of the refractive index suggest that this material is more suitable for optical waveguides applications.

Atomic layer deposition of ZnO thin film on surface modified monolayer MoS2 with enhanced photoresponse

Monolayer MoS2 was grown on a sapphire substrate by CVD, and then transferred to a silicon wafer substrate. The morphology and crystalline of the MoS2 were characterized by AFM, SEM, and XRD. After perylene-3,4,9,10-tetracarboxylic acid (PTCA) surface treatment on the MoS2, a continuous layer of ZnO thin film was deposited. Finally, the photoresponse of both ZnO and ZnO/MoS2 thin films was investigated, and the ZnO/MoS2 thin film showed enhanced photoresponse over pure ZnO thin film. The higher response of ZnO/MoS2 hetero-structure could be attributed to the effective charge transfer between ZnO and MoS2 surface and the re-absorption of light photon resulting in the production of electron-hole pairs.

Scalable Wet Deposition of Zeolite AEI with a High Degree of Preferred Crystal Orientation

AbstractProducing zeolite films with controlled preferred orientation on an industrial scale is a long‐standing challenge. Herein we report on a scalable approach to the direct wet deposition of zeolite thin films and membranes while maintaining a high degree of control over the preferred crystal orientation. As a proof of concept, thin films comprising aluminophosphate zeolite AEI were cast on silicon wafer or porous alumina substrates. Electrical properties and separation performance of the zeolite thin films/membranes were engineered through controlling degree of preferred crystal orientation.

Scalable Wet Deposition of Zeolite AEI with a High Degree of Preferred Crystal Orientation.

Producing zeolite films with controlled preferred orientation on an industrial scale is a long-standing challenge. Herein we report on a scalable approach to the direct wet deposition of zeolite thin films and membranes while maintaining a high degree of control over the preferred crystal orientation. As a proof of concept, thin films comprising aluminophosphate zeolite AEI were cast on silicon wafer or porous alumina substrates. Electrical properties and separation performance of the zeolite thin films/membranes were engineered through controlling degree of preferred crystal orientation.

Effect of Bias Applied to the Substrate on the Low Temperature Growth of Silicon Epitaxial Films during RF-PECVD

The deposition behavior of silicon films by radio frequency plasma-enhanced chemical vapor deposition (RF-PECVD) was studied by nonclassical crystallization, where the building block of deposition is charged nanoparticles generated in the gas phase of the reactor. To confirm the existence of nanoparticles in the RF-CVD reactor, nanoparticles were captured on the membrane of the transmission electron microscope (TEM) grid under the condition of the DC bias applied to the holder. The capturing behavior of nanoparticles depended on the bias and the conductivity of the membrane. Also, to examine the effect of the bias on the epitaxial growth, films were deposited on the silicon wafer substrate under the condition of the biases of 0, +1000, and −1000 V applied to the substrate holder. A fully epitaxial film could be grown on a silicon wafer at 550 °C under the bias of −1000 V.

Multi-pulsed flash light sintering of copper nanoparticle pastes on silicon wafer for highly-conductive copper electrodes in crystalline silicon solar cells

In this work, ultra-high speed flash white light (FWL) sintering method of copper nanoparticle pastes on silicon wafer substrate, was developed to produce highly conductive and low-cost copper electrodes for crystalline silicon solar cells. FWL sintering of copper nanoparticles on silicon wafer substrate has been regarded to be very difficult, due to its high thermal conductivity (k) compared with that of polymer (PI and PET) substrates. To overcome this limitation, we applied multiple pulsed FWL to sinter copper nanoparticles (Cu NPs) printed on silicon wafer. Furthermore, bimodal Cu NPs with different size were also applied to enhance the packing density of Cu films for highly conductive Cu electrodes. Finally, this work demonstrated that Cu NP-pastes are successfully sintered on crystalline silicon wafer substrate by multiple pulsed FWL irradiations.

Surface Modification of Carbon Fibres for Interface Improvement in Textile Composites

The performance of carbon fibre-reinforced composites is dependent to a great extent on the properties of fibre-matrix interface. In this research, based on the reviewed surface modification technique and inspired by the in situ growth of three-dimensional graphene coatings on nanomaterials, a new method of in situ growth of a graphene-related structure on the surface of carbon fibres is to be applied, for which it is intended to use a mixed solution of Ferrous Sulfate Heptahydrate (FeSO4· 7H2O) and D-Glucose monohydrate (C6H12O6 · H2O) to treat the carbon fibres under specific conditions to in-situ growth of a graphene-related coatings on the surface of carbon fibres. Firstly, the method was carried out by heating the mixed solution under specific temperature on the silicon wafer substrate and followed with characterisation experiments such as Raman and Scanning Electron Microscopy (SEM). Then, the mixed solution was applied on the carbon fibres and treated under the same condition. The characterisation results indicated successfully growth of the porous carbon coatings on the surface of the carbon fibres, which contained with graphene-related structures, while other characterization experiment like Transition Electron Microscopy (TEM) and X-ray Photoelectron Spectroscopy (XPS) will need to be used to further characterise the porous carbon structure. The interfacial shear strength between the fibre and the porous carbon coating also need to be characterised by using the micro-bond test.