Single Crystal Silicon Substrates Research Articles

Internal mechanical stresses and the thermodynamic and adhesion parameters of the metal condensate-single-crystal silicon system

The kinetics of generation of internal mechanical stresses σ(d) in chromium, copper, gold, and aluminum thin films on single-crystal silicon substrates at different deposition rates has been experimentally investigated using the cantilever method. A two-step character of the variations in internal tensile stresses has been revealed. The regularities of the formation of the maximum level of mechanical stresses in the condensates under investigation have been established. The energy and adhesion parameters of chromium, copper, gold, and aluminum nanolayers on silicon, germanium, and nickel substrates have been studied using the macroscopic methods of surface physics. The interfacial energy, interfacial tension, work of adhesion, interfacial charge, and a new energy characteristic of the interfacial layer, namely, the energy of adhesive bonds, which exceeds the interfacial energy, have been determined.

Ba0.8Sr0.2TiO3 ferroelectric nanofilms on silicon buffered with a TiO2 layer

Polycrystalline, 50- to 70-nm-thick barium strontium titanate films of composition Ba0.8Sr0.2TiO3 have been grown on single-crystal silicon substrates by rf ion-beam sputtering. We have determined their structure and composition and detected impurities at the film/substrate interface in the form of titanium silicide islands. The deposition of a 4- to 6-nm-thick TiO2 buffer layer onto Si by ion-beam sputtering before ferroelectric film growth is shown to prevent uncontrolled formation of impurities near the interface. The buffered heterostructures possess high thermal stability.

X-Ray Reflectivity and Diffuse Scattering Study of Effect of Ca2+ on Cushioned Lipid Bilayer

The effects of Ca2+ on bio-membranes are of interest because of their role in several biological processes, including facilitating the membrane fusion process. In a recent study, we have investigated a cushioned [1] DPPC bilayer in water and in different concentration CaCl2 solutions via fluid exchange. We used a polymer (PAA) cushion deposited on a single crystal silicon substrate. Using a 22 keV X-ray beam at the beamline of Sector 8 at the Advanced Photon Source, we obtained high resolution reflectivity from the bilayer and cushion through water, and were also able to study the grazing incidence x-ray diffuse scattering. The effect of Ca2+ on the bilayer structure has been obtained from the reflectivity analysis, which shows the Ca2+ ions binding to the headgroups of outer leaflet of the DPPC bilayer. The diffuse scattering is used to obtain the physical properties such as the surface tension, bending modulus, etc. Combining both, we present a complete picture of how Ca2+ affects a DPPC bilayer in water at room temperature as a function of Ca2+ concentration.

Comparison between metal ion and polyelectrolyte functionalization for electrophoretic deposition of graphene nanosheet films

Graphene nanosheets (GNSs) were modified either by metal magnesium (Mg) ions or a polyelectrolyte, polydiallyldimethylammonium chloride (PDDA), to produce positive charges on them. The two materials were used to produce GNS films with different surface morphologies. They were deposited on single-crystal silicon substrates using simple direct current electrophoretic deposition method. The Mg ion-modified GNS film has a relatively rough surface with some GNSs almost perpendicular to the surface, whereas the PDDA-modified GNS film has a relatively smooth surface with most GNSs parallel to the substrate. This difference is attributed to the different interactions of Mg ions and PDDA molecules with GNSs. Because of the favorable surface morphology, the Mg ion-modified GNS film displays better field emission compared with the PDDA-modified GNS film. Biocompatibility tests indicate that the rougher Mg ion-modified GNS film is more beneficial to cell adhesion and growth.

生长温度对Ga掺杂ZnO薄膜光电性能的影响

Gadoped ZnO(GZO) thin films were grown on single crystal silicon(111) and quartz glass substrates by pulsed laser deposition(PLD) method at different substrate temperatures from room temperature to 750 ℃.The change of substrate temperature leads to different diffusion and desorption rates for adsorption atoms resting on substrate surface,and results in different crystalline quality for GZO thin films.The GZO thin film grown at 450 ℃ has the best crystalline quality.The carrier concentration monotonically decreases with the increase of substrate temperature,which is related to the intrinsic defects in films.The Hall mobility first increases and then decreases with the substrate temperature increasing,it results from the variation of grain boundary scattering.And the lowest resistivity ~0.02 Ω·cm is obtained in the film prepared at 450 ℃.With the increase of substrate temperature,the optical band gap becomes narrow due to the monotonic increase of carrier concentration.The average transmittance in visible region is above 85% for all the GZO samples.Our results exhibit that the optical and electrical properties of GZO thin films prepared by PLD method can be adjusted by the change of substrate temperature.

Crystalline growth of germanium thin films on single crystal silicon substrates by solid phase crystallization

We have studied the epitaxial-like growth of germanium (Ge), due to solid phase crystallization (SPC) from amorphous Ge (a-Ge) deposited on single crystal silicon (Si) substrate. The crystalline growth of Ge following the orientation of Si substrates was successfully obtained by the SPC at 400°C or higher. The preferential growth on Si (111) substrates continues up to 10,000Å. Different orientations from the substrate orientation in XRD patterns are slightly observed in the growth on Si (100) substrates at 450°C, but the preferential growth of (100) orientation continued in the whole film thickness in TEM images. The epitaxial-like growth of Ge may be more preferable on the Si (111) substrate than the (100) one.

Layer-by-layer assembly and tribological property of multilayer ultrathin films constructed by modified graphene sheets and polyethyleneimine

A series of graphene sheets (GS)-based multilayer films was constructed in virtue of layer-by-layer electrostatic self-assembly technique based on the negatively charged poly(sodium 4-styrenesulfonate) (PSS) mediated GS (PSS-GS) and the positively charged polyethyleneimine (PEI). High-resolution transmission electron microscope, atomic force microscope and micro-Raman spectrum characterizations demonstrated that the PSS-GS has been synthesized and could be assembled on the single-crystal silicon substrate. Ellipsometric thickness measurement and ultraviolet–visible absorption spectroscope confirmed the successive assemblies of GS. Finally, the macrotribological behaviors of different multilayer films were evaluated on a ball-on-plate macrotribometer and the results indicated that the prepared three- and five-layer films had high load affording ability and long anti-wear life, which could be highly dependent upon the high coverage and excellent self-lubricant properties that the GS owns intrinsically.

Investigation of induced parallel magnetic anisotropy at low deposition temperature in Ba-hexaferrites thin films

In this paper we present the effect of low substrate temperature on structural, morphological, magnetic and optical properties of Ba-hexaferrite thin films. Films were deposited on single crystal Silicon (100) substrate employing the Pulsed Laser Deposition (PLD) technique. The structural, morphological, magnetic and optical properties are found to be strongly dependent on substrate temperature. The low substrate temperatures (room temperature to 200°C) restrict the formation of larger grains. For the higher substrate temperature i.e., 400°C, the grain size of the deposited thin film are much larger. The film grown at low substrate temperature do not show any anisotropy. As the substrate temperature is increased, the easy axis of the films alinged itself in the direction parallel to the film plane whereas the hard axis remained in the perpendicular direction. The higher substrate temperature caused the uniaxial magnetic anisotropy, which is very important in magnetic recording devices. The saturation magnetization and optical band gap energy values of 62emu/cc and 1.75eV, respectively, were achieved for the film of thickness 500nm deposited at 400°C. Higher values of coercivity, squareness and films thickness are associated with the growth of larger grains at higher substrate temperature.

Growth and structure of Mg(Fe0.8Ga0.2)2O4 − δ films

Films 150–200 nm in thickness, with the nominal composition Mg(Fe0.8Ga0.2)2O4 − δ have been grown on (100) single-crystal silicon substrates by ion-beam sputtering in vacuum. The effect of growth and annealing conditions on the crystal structure and morphology of the films has been studied, and the thermal conditions for the growth of spinel-structure films have been optimized.

Thermal conductivity measurement of porous silicon by the pulsed-photothermal method

Thermal properties of two types of porous silicon are studied using the pulsed-photothermal method (PPT). This method is based on a pulsed-laser source in the nanosecond regime. A 1D analytical model is coupled with the PPT technique in order to determine thermal properties of the studied samples (thermal conductivity and volumetric heat capacity).At first, a bulk single crystal silicon sample and a titanium thin film deposited on a single crystal silicon substrate are studied in order to validate the PPT method. Porous silicon samples are elaborated with two different techniques, the sintering technique for macroporous silicon and the electrochemical etching method for mesoporous silicon. Metallic thin films are deposited on these two substrates by magnetron sputtering. Finally, the thermal properties of macroporous (30% of porosity and pores diameter between 100 and 1000 nm) and mesoporous silicon (30% and 15% of porosity and pores diameter between 5 and 10 nm) are determined in this work and it is found that thermal conductivity of macroporous (73 W m−1 K−1) and mesoporous (between 80 and 50 W m−1 K−1) silicon is two times lower than the single crystal silicon (140 W m−1 K−1).

A Low-Cost CMOS-MEMS Piezoresistive Accelerometer with Large Proof Mass

This paper reports a low-cost, high-sensitivity CMOS-MEMS piezoresistive accelerometer with large proof mass. In the device fabricated using ON Semiconductor 0.5 μm CMOS technology, an inherent CMOS polysilicon thin film is utilized as the piezoresistive sensing material. A full Wheatstone bridge was constructed through easy wiring allowed by the three metal layers in the 0.5 μm CMOS technology. The device fabrication process consisted of a standard CMOS process for sensor configuration, and a deep reactive ion etching (DRIE) based post-CMOS microfabrication for MEMS structure release. A bulk single-crystal silicon (SCS) substrate is included in the proof mass to increase sensor sensitivity. In device design and analysis, the self heating of the polysilicon piezoresistors and its effect to the sensor performance is also discussed. With a low operating power of 1.5 mW, the accelerometer demonstrates a sensitivity of 0.077 mV/g prior to any amplification. Dynamic tests have been conducted with a high-end commercial calibrating accelerometer as reference.

Research on Annealing Temperature of SiO<sub>2</sub> on Si Substrate

Silicon dioxide films; radio-frequency magnetron sputtering; annealing temperature Abstract. Silicon dioxide (SiO2) films are fabricated on single crystal silicon substrate by radio-frequency magnetron sputtering (RFMS) technique and annealed in electric furnaces at 800°C and 1180°C to form uniform, transparent and compact silica. The surface morphology and roughness of the films are characterized by an atomic force microscopy (AFM). X-ray diffraction (XRD) is employed to analyze the crystalline of the thin films. The chemical composition after annealing is analyzed using X-ray photoelectron spectroscopy (XPS).

Preparation and Characteristics of Nanocrystalline Diamond Film by Using of MPVCD

With the microwave plasma chemical vapor deposition (MPCVD), the effects of the deposition pressure and the different substrate temperature on diamond coating on single crystal silicon substrate were studied systemically. The sample was characterized by means of scanning electron microscopy (SEM) and laser Raman spectra (Raman). The experimental results showed that the surface of the film was compact, the mean particle diameter was 98nm, and that it contains thesp3carbon phase with good quality.

Study on Compound Machining of Polyurethane Polishing Pad and Cluster Abrasive Brush Based on MR Effect

Method of compound machining is used to process single crystal silicon and SrTiO3 ceramic substrates, and the factors on effects of compound machining are studied such as magnetic field intensity, processing time, rotating speed of lapping plate and lapping pressure. The results show that the roughness of work pieces processed by compound machining are smaller than that by lapping based on cluster MR effect and polyurethane pad polishing process, while the material removal rate is higher than polyurethane pad polishing process, therefore, compound machining shows its synergistic effect between lapping based on cluster MR effect and polyurethane pad polishing process. The type and properties of workpiece material, and machining parameters both have a significant impact on the roughness and material removal rate of compound machining process of polyurethane polishing pad and cluster abrasive brush based on MR effect.

Structure Design, Fabrication and Characteristics of Polysilicon Nano-Thin Films Resistances Pressure Sensor Based on MEMS Technology

A polysilicon nano-thin films pressure sensor was designed and fabricated on single crystal silicon substrate by MEMS technology in this paper, and the sensor is composed by Wheatstone bridge structure with four polysilicon nano-thin films resistances fabricated on squared silicon membrane. The experiment result shows that, under constant current power supply of 0.875mA , full scale output is 24.05 mV at room temperature, sensitivity is 0.15 mV/kPa, when the temperatures are from -20 to 80°C, the coefficient of zero temperature and sensitivity temperature is –960 ppm/°C and –820 ppm /°C respectively.

Study on tribological property of CrCN coating based on magnetron sputtering plating technique

The influence of carbon doping on tribological properties of CrCN coating was studied through preparation of coatings deposited on single crystal silicon and M2 high-speed steel (HSS) substrate using closed-field unbalanced magnetron sputtering ion plating technique. The friction coefficients were measured by pin-on-disc set-up and the wear traces of the coatings were observed by optical microscope. The microstructure and bond states of the coatings were characterized by atomic force microscope (AFM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The results show that the friction coefficient of coating decreases from 0.75 to 0.38, the micro-hardness increases from 1930 HV to 2300 HV, and the specific wear ratio of the coatings decreases from 8.351 × 10 −15 m 3/Nm to 3.859 × 10 −15 m 3/Nm with the increasing of carbon target current ( I C ) from 0 A to 1.5 A. The grain size and the roughness of the coatings both decrease with the increasing of carbon target current, at the same time the coatings transform from crystalline state to amorphous state.

Fracture Transfer of Vertical Semiconductor Pillar Arrays to Low Cost Arbitrary Substrates for Flexible Energy Device Applications

ABSTRACTIn this paper, we demonstrate a heterogeneous integration technique that preserves the integrity, order, shape, and fidelity of vertically aligned single-crystal semiconductor micro- and nano- pillars by harvesting and transferring them from a single crystal substrate to a low-cost carrier substrate. The mechanism of the transfer technique exploits a combination of vertical embossing and lateral fracturing of the crystalline pillars with the assistance of a spin-coated polymer layer on a carrier substrate as well as facilitating multilayer process device integration. Specifically, the novel use of a water soluble adhesive polymer from MasterBond that acts simultaneously as a mechanical transfer polymer and as a sacrificial harvest layer further expands the versatility of this approach. Arrays of vertical micropillars of average height ~15)μm and diameter ~1.5μm on a die silicon substrate of 5mm x 5mm were fabricated via transformative top-down approaches (DRIE) on a single crystal silicon substrate and then transferred to a different target carrier substrate using the adhesive polymer assisted bendingfracturing process. The adhesive polymer is odorless, non-conducting, easy to process, spincoatable, optically transparent, resistant to heat, high mechanical strength and easily cures at room temperature. The original pillar wafers may be used repeatedly after polishing for generating more devices and are minimally consumed. Low contact resistances are formed for electrical addressing using metals and conducting thermoplastics of Ag nanoparticles. This heterogeneous integration technique potentially offers enhanced photon semiconductor interactions, while enabling multimaterial integration such as silicon with compound semiconductors (InP, GaAs etc.) for applications, including high speed electronics, low-cost and flexible electronics, displays, tactile sensors, and energy conversion systems.

Temperature-dependent growth mechanisms of low-dimensional ZnO nanostructures

One-dimensional ZnO nanostructures were successfully synthesized on single-crystal silicon substrates via a simple thermal evaporation and vapour-phase transport method under different process temperatures from 500 to 1000 °C. The detailed and in-depth analysis of the experimental results shows that the growth of ZnO nanostructures at process temperatures of 500, 800, and 1000 °C is governed by different growth mechanisms. At a low process temperature of 500 °C, the ZnO nanostructures feature flat and smooth tips, and their growth is primarily governed by the vapour-solid mechanism. At an intermediate process temperature of 800 °C, the ZnO nanostructures feature cone-shape tips, and their growth is primarily governed by the self-catalyzed and saturated vapour–liquid–solid mechanism. At a high process temperature of 1000 °C, the alloy tip appears on the front side of the ZnO nanostructures, and their growth is primarily governed by the common catalyst-assisted vapour–liquid–solid mechanism. It is also shown that the morphological, structural, optical, and compositional properties of the synthesized ZnO nanostructures are closely related to the process temperature. These results are highly relevant to the development of light-emitting diodes, chemical sensors, energy conversion devices, and other advanced applications.

Fabrication of Sub-5 nm Nanochannels in Insulating Substrates Using Focused Ion Beam Milling

The use of focused ion beam (FIB) milling to fabricate nanochannels with critical dimensions extending below 5 nm is described. FIB milled lines have narrowing widths as they are milled deeper into a substrate. This focusing characteristic is coupled with a two-layered architecture consisting of a relatively thick (>100 nm) metal film deposited onto a substrate. A channel is milled through the metal layer until it penetrates a prescribed depth into the substrate material. The metal is then removed, leaving a nanochannel with smooth surfaces and lateral dimensions as small as sub-5 nm. These open nanochannels can be sealed with a cover plate and the resulting devices are well-suited for single-molecule DNA transport studies. This methodology is used with quartz, single-crystal silicon, and polydimethylsiloxane substrates to demonstrate its general utility.

Photothermoacoustic conversion in porous matrix-liquid filler systems

Features of the photothermoacoustic conversion in systems of the porous silicon-liquid filler type on a single crystal silicon substrate have been experimentally studied. It is established that the presence of liquid in the pores leads to a significant increase in the photoacoustic signal amplitude and front slope, which is explained by a significant contribution of the liquid pressure to thermoinduced stresses in the material. The extrema observed in time series of the photoacoustic signal in the case of a low-viscosity liquid are related to the process of pressure relaxation in the pores.