Monocrystalline Silicon Substrates Research Articles

In silico monitoring of non-reactive gas blistering on crystalline substrates

Blistering from gas aggregation occurs very rarely on solid substrates; however, it is commonly observed under high-pressure gas or plasma environments. This is due to the repeated aggregation process of gas molecules penetrating beneath the surface, but it has been difficult to find cases that demonstrate the dynamic mechanism on the atomic level. In this study, the dynamics of physical bombardment of argon atoms on the flat monocrystalline silicon substrate are simulated to propose an initiation principle for gas-aggregate formation. Simulations of extremely large numbers of argon atoms bombarding a limited area of single crystal silicon revealed inhomogeneous aggregation properties consistent with the experimental observations. Particularly, the results suggest that momentum transfer formed by collisions between argon trapped in the surface grooves and the argon used for bombardment is the governing factor for the aggregation behavior. The aggregated argon clusters grow in the in-plane direction while generating stress propagation in the thickness direction, ultimately causing an expansion pressure that lifts the adjacent silicon surface upwards. Our work provides a deterministic understanding of the initiation process of blister formation, which rarely occurs in physical sputtering on defect-free substrates.

Assessing the Aging Effect on Ti/Au Bilayers for Transition-Edge Sensor (TES) Detectors.

Transition-edge sensor (TES) microcalorimeters are advanced cryogenic detectors that use a superconducting film for particle or photon detection. We are establishing a new production line for TES detectors to serve as cryogenic anticoincidence (i.e., veto) devices. These detectors are made with a superconducting bilayer of titanium (Ti) and gold (Au) thin films deposited via electron beam evaporation in a high vacuum condition on a monocrystalline silicon substrate. In this work, we report on the development of such sensors, aiming to achieve stable sensing performance despite the effects of aging. For this purpose, patterned and non-patterned Ti/Au bilayer samples with varying geometries and thicknesses were fabricated using microfabrication technology. To characterize the detectors, we present and discuss initial results from repeated resistance-temperature (R-T) measurements over time, conducted on different samples, thereby augmenting existing literature data. Additionally, we present a discussion of the sensor's degradation over time due to aging effects and test a potential remedy based on an easy annealing procedure. In our opinion, this work establishes the groundwork for our new TES detector production line.

The Influence of B4C Film Density on Damage Threshold Based on Monte Carlo Method for X-ray Mirror.

The uniformity and consistency of X-ray mirror film materials prepared by experimental methods are difficult to guarantee completely. These factors directly affect the service life of free electron laser devices in addition to its own optical properties. Therefore, the quality of the film material, especially the density, has a critical effect on its application. Boron carbide film and monocrystalline silicon substrate were suitable examples to explore their influence of density on the damage threshold based on Monte Carlo and heat-conduction methods. Through simulation results, it was found that the change in film density could affect the energy deposition depth and damage threshold. When the film density was 2.48 g/cm3, it had relatively high damage threshold in all energy ranges. And then the specific incident parameter for practical application was investigated. It was found that the damage mechanism of the B4C/Si was the melting of the interface. And the damage threshold was also higher with the film density of 2.48 g/cm3. Therefore, it was recommended to maintain the density at this value as far as possible when preparing the film, and to ensure the uniformity and consistency of the film material.

Nanoindentation-induced interface behavior between DLC film and monocrystalline silicon substrate at high temperature: A molecular dynamics simulation study

Diamond-like carbon (DLC) film is an excellent protective coating material, which has a wide range of applications. The interface behavior between around 1 nm DLC film and the monocrystalline silicon substrate is difficult to characterize through experiments. In this work, the nanoindentation molecular dynamics simulations are performed to investigate the interface behavior between DLC film and the silicon substrate at high temperature. A method for determining the depth of indentation has been proposed. As the temperature increases, the maximum repulsive force between indenter and DLC film decreases, the maximum adhesive force increases. High atomic shear strains locate at the interface between DLC and monocrystalline silicon during indentation process. High temperature enlarges the atomic strain distribution region. The number of holes in the monocrystalline silicon substrate increases with increase of temperature after indentation process. The evolution processes of silicon atomic structures have been revealed. Both the repulsive force and adhesive force in the indentation process contribute the silicon phase transformation. But the final silicon atom bonding structure and pop-out phenomena are determined by the adhesive force during the unloading process.

Effect of rapid thermal annealing on the surface properties of the microlens arrays machined on monocrystalline silicon

Microstructure arrays, such as microlens arrays, play a significant role in optical systems, biomedical imaging, and telecommunications. However, the machining-induced subsurface defects deteriorate their performance and functionality. To address this issue, this study proposes a rapid thermal annealing method to heal the subsurface defects using different temperatures ranging from 200 °C to 1000 °C in a vacuum. Firstly, the ultra-precision diamond sculpturing process is employed to machine the high-quality microlens array on the monocrystalline silicon surface. Then, the effects of the rapid thermal annealing on the microlens array surface, such as surface roughness and subsurface defect, are comprehensively investigated. Experimental results show that the annealing temperature of >600 °C contributes to the decrease in surface roughness and subsurface defect. Furthermore, to reveal the healing mechanism, a molecular dynamics simulation of rapid thermal annealing is performed by controlling the bulk temperature of machined monocrystalline silicon from 500 K to 1300 K. The simulation results show that recrystallization always occurred on the interface between the amorphous layer and monocrystalline silicon substrate and the healing mechanism should be solid phase epitaxy rather than random nucleation. The research findings would contribute to fabricating the defect-free optical lens in the industry.

Characterization of Chiral Nanostructured Surfaces Made via Colloidal Lithography.

Optically anisotropic materials were produced via colloidal lithography and characterized using scanning electronic microscopy (SEM), confocal microscopy, and polarimetry. A compact hexagonal array mask composed of silica sub-micron particles was fabricated via the Langmuir-Blodgett self-assembly technique. Subsequently, the mask pattern was transferred onto monocrystalline silicon and commercial glass substrates using ion beam etching in a vacuum. Varying the azimuthal angle while etching at oblique incidence carved screw-like shaped pillars into the substrates, resulting in heterochiral structures depending on the azimuthal angle direction. To enhance the material's optical properties through plasmon resonance, gold films were deposited onto the pillars. Polarimetric measurements were realized at normal and oblique incidences, showing that the etching directions have a clear influence on the value of the linear birefringence and linear dichroism. The polarimetric properties, especially the chiroptical responses, increased with the increase in the angle of incidence.

High entropy alloy thin films on SS304 substrates: Evolution of microstructure and interface modulated by energetic condensation in nanoscale

High entropy alloys (HEAs), as a novel material in the 21st century, possess several advantages, such as excellent corrosion & oxidation resistance and high mechanical properties. HEA thin films show these favourable properties with lower material costs than their bulk counterparts. Studying the HEA film-substrate interface represents challenges but is of extreme importance for the understanding of growth mechanisms with important implications for film adhesion. However, most HEA films were deposited on monocrystalline silicon substrates with limited practical applicability. Further, where commercial stainless steel, aluminium or titanium alloy substrates were used, the microstructure and chemistry at the interface were neglected. Here, we deposited AlCrFeCoNiCu0.5 HEA thin films on stainless steel 304 (SS304) substrates using cathodic arc deposition with different substrate biases. The crystallography and microstructure were investigated using an X-ray and electron-microscopy based chatacterization. A transition of an incoherent to semi-coherent interface was observed from 0 V to -50 V of the substrate bias. Energy dispersive spectroscopy demonstrated a transition of Cr2O3 to aluminum oxide across the interface. The nanoindentation tests revealed the significant improvement of mechanical properties of SS304 with HEA coatings. High-strength HEA (8.0 ± 0.2 GPa) thin films with semi-coherent interfaces were manufactured on SS304.

First Sharp Diffraction Peak features of the intermediate phase glasses and amorphous thin films in the non-stoichiometric (GeS4)x(AsS3)1-x system

Grazing incidence X-ray scattering (GIXRS) patterns of thin solid films based on non-stoichiometric chalcogenide glasses (ChG) from the pseudo - binary system (GeS4)x(AsS3)1-x were studied with a focus on the First Sharp Diffraction Peak (FSDP), assigned to the middle range order (MRO) of the glassy material. The films were grown using explosive thermal evaporation in vacuum (10−4 Pa) of pulverized ChG, prepared from previously synthesized bulk glasses, onto mono-crystalline silicon substrates. Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray (EDX) spectroscopy were used to examine the morphology and elemental composition of the films, which were found to have similar composition to the bulk glasses. However, it was revealed that the molecular structure of the grown amorphous films differs from that of the initial ChG bulk material, as indicated by changes in the composition-dependent position and width of the FSDP. Additionally, the intensities of the FSDP in the films were higher compared to those of the bulk samples, suggesting that the molecular-like structure of ChGs is more pronounced in the form of thin films grown from the vapor phase.

Synthesis of arrays nanostructured porous silicon wires in electron conductivity type silicon with crystallographic orientation (111)

The method of modified metal-assisted electrochemical etching was proposed and arrays of nanostructured porous silicon wires on n-type monocrystalline silicon substrate with crystallographic orientation (111) were obtained. The influence of the electrolyte composition at the second stage of obtaining on the morphology of silicon wires by scanning electron microscopy methods was revealed. The phase composition of porous silicon wires was controlled by Raman spectroscopy. Keywords: Porous silicon,porous Silicon nanowires, MACE, Nanomaterials, Raman spectroscopy.

Синтез массивов наноструктурированных пористых кремниевых стержней в кремнии электронного типа электропроводности с кристаллографической ориентацией (111)

The method of modified metal-assisted electrochemical etching was proposed and arrays of nanostructured porous silicon wires on n-type monocrystalline silicon substrate with crystallographic orientation (111) were obtained. The influence of the electrolyte composition at the second stage of obtaining on the morphology of silicon wires by scanning electron microscopy methods was revealed. The phase composition of porous silicon wires was controlled by Raman spectroscopy.

RAMAN SPECTRА OF SILICON/GERMANIUM ALLOY THIN FILMS BASED ON POROUS SILICON

The regularities of composition changes of silicon/germanium alloy thin films formed on a monocrystalline silicon substrate by electrochemical deposition of germanium into a porous silicon matrix with subsequent rapid thermal annealing (RTA) at a temperature of 750–950°C are studied. An analysis of the samples by Raman spectroscopy showed that an increase of RTA temperature leads to a decrease in the germanium concentration in the formed film. A decrease of the RTA duration at a given temperature makes it possible to obtain films with a higher concentration of germanium and to control the composition of thin silicon/germanium alloy films formed by changing the temperature and duration of RTA. The obtained results on controlling the composition of silicon/germanium alloy films can be used to create functional electronic devices, thermoelectric power converters, and optoelectronic devices.

FORMATION AND ELECTROCHEMICAL PROPERTIES OF NICKEL AND COBALT TRANSITION METALS OXIDE FILMS

Films of cobalt oxide and nickel oxide on monocrystalline silicon substrates were obtained by electrochemical deposition from aqueous electrolyte solutions. Their structure and composition were studied by Raman microscopy and scanning electron microscopy. The results of the study by Raman spectroscopy showed that the obtained films are polycrystalline structures of cobalt (II, III) oxide and nickel (II) oxide, the crystalline perfection of which increases with an increase in the electrolyte temperature. It was found by scanning electron microscopy that nickel oxide films have a smoother surface, while cobalt oxide has a more developed structure consisting of lamellar crystals. The specific electrochemical capacity of cobalt oxide and nickel oxide films obtained under optimal conditions, measured by voltammetry, was 14.67 and 1634.08 F/g, respectively. The high specific electrochemical capacity of a nickel oxide film can be used to create efficient electrochemical devices and energy storage devices.

Chemical Vapor Deposition of 2D Crystallized g-C3N4 Layered Films

We have developed a technology and for the first time, present here, the fabrication of continuous two-dimensionally crystallized g-C3N4 layered thin films oriented in a hexagonal lattice c-plane on glass and monocrystalline silicon substrates using chemical vapor deposition from a melamine source. Scanning electron microscopy and X-ray diffraction studies revealed that such films with a smooth surface and good crystalline quality as thick as up to 1.2 μm can be formed at a synthesis temperature of 550–625 °C. They are transparent in the visible range and demonstrate intense photoluminescence (PL) at room temperature. It was found that the band gap of the obtained material and its PL spectral range are shifting to the lower energies at high synthesis temperatures. Oriented g-C3N4 layered thin films deposited on flat solid substrates are promising for integrated electronics and optoelectronics.

Формирование нанокристаллов и аморфных нанокластеров германия в пленках GeO[SiO] и GeO[SiO-=SUB=-2-=/SUB=-] с использованием электронно-пучкового отжига

Electron beam annealing was carried out to form amorphous and crystalline germanium clusters in GeO[SiO] and GeO[SiO2] films deposited on quartz and monocrystalline silicon substrates. Using electron microscopy, Raman spectroscopy, and light transmission and reflection spectroscopy, the structural transformations of the films and their optical properties were studied. From the analysis of Raman spectra, it was shown that amorphous germanium nanoclusters are present in the initial GeO[SiO] film, while they are not observed in the initial GeO[SiO2] film. Regimes of electron-beam annealing which are necessary for the formation of germanium nanocrystals in GeO[SiO] and GeO[SiO2] films were found. It was shown that, at the same annealing parameters, the fraction of the crystalline phase of germanium in GeO[SiO] films were smaller than in GeO[SiO2] films. In addition, it was found that the fraction of the crystalline phase at the same annealing parameters is larger for films on a quartz substrate than on monocrystalline silicon substrate. The sizes of germanium nanocrystals formed as a result of electron beam annealing were determined from Raman spectra analysis. The proposed method of obtaining amorphous germanium nanoclusters and nanocrystals in films of nonstoichiometric germanosilicate glasses using electron beam annealing can be used to create ordered arrays of such nanostructures.

Formation of germanium nanocrystals and amorphous nanoclusters in GeO[SiO] and GeO[SiO-=SUB=-2-=/SUB=-] films using electron beam annealing

Electron beam annealing was carried out to form amorphous and crystalline germanium clusters in GeO[SiO] and GeO[SiO2] films deposited on quartz and monocrystalline silicon substrates. Using electron microscopy, Raman spectroscopy, and light transmission and reflection spectroscopy, the structural transformations of the films and their optical properties were studied. From the analysis of Raman spectra, it was shown that amorphous germanium nanoclusters are present in the as-deposited GeO[SiO] film, while they are not observed in the as-deposited GeO[SiO2] film. Regimes of electron beam annealing which are necessary for the formation of germanium nanocrystals in GeO[SiO] and GeO[SiO2] films were found. It was shown that, at the same annealing parameters, the fraction of the crystalline phase of germanium in GeO[SiO] films were smaller than in GeO[SiO2] films. In addition, it was found that the fraction of the crystalline phase at the same annealing parameters is larger for films on a quartz substrate than on monocrystalline silicon substrate. The sizes of germanium nanocrystals formed as a result of electron beam annealing were determined from Raman spectra analysis. The proposed method of obtaining amorphous germanium nanoclusters and nanocrystals in films of nonstoichiometric germanosilicate glasses using electron beam annealing can be used to create ordered arrays of such nanostructures. Keywords: films of nonstoichiometric germanosilicate glass, electron beam annealing, germanium nanoclusters and nanocrystals.

Фазовые переходы в эпитаксиальных слоях карбида кремния, выращенных на кремниевой подложке методом согласованного замещения атомов

Temperature dependences of the longitudinal resistance and heat capacity of silicon carbide epitaxial films grown on monocrystalline silicon substrates by the method of coordinated substitution of atoms are investigated. Peculiarities in the behavior of these dependences have been found at temperatures equal to 56°C, 76°C, 122°C and 130°C. The observed peculiarities of the behavior of heat capacity and longitudinal resistance, considering appearance of a giant value of diamagnetism previously discovered in the samples at these temperatures, are interpreted as phase transitions of charge carriers into a coherent (superconducting, if we consider diamagnetism) state.

Influence of synthesis parameters and thermal annealing on grain size of polycrystalline aluminum thin film

The thin polycrystalline aluminium films were synthesized on monocrystalline silicon substrates by ion-plasma sputtering. The synthesis was carried out at temperatures of 80 and 160°C and deposition rate of 10 and 110 nm/min. As-deposited films were annealed for 15 h at 550°C. The morphology of aluminium films before and after annealing was obtained using SEM images. The surfaces of as-deposited Al thin films, synthesized at high temperature, were uneven, while for low temperature films they were smooth enough with Al hillocks on the top of the film. After thermal annealing, morphology of the films was changed slightly. XRD patterns were obtained to calculate the average Al grain size of as-deposited and annealed films. The XRD analysis showed that an increase in the synthesis temperature leads to an increase in the average grain size from 50 to 84 nm and that increase in the rate of Al film synthesis leads to an increase in the average grain size from 50 to 63 nm. As the result of annealing, the average grain size increased for all samples and the final meaning was from 78 to 140 nm.

On the limiting efficiency for silicon heterojunction solar cells

Silicon heterojunction (SHJ) solar cell, as one of the promising technologies for next-generation passivating contact solar cells, employs an undiffused and n-type mono-crystalline silicon (c-Si) substrate and two amorphous-silicon-based selective contacts with opposite polarities. In this work, a numerical model based on Richter's theory has been developed to simulate the performances of a 25.11 % efficiency SHJ solar cell obtained recently. Analyses on series resistivity (Rs) explicit that the upper bound for the sum of contact resistivities for p-type (ρc,p) and n-type (ρc,n) contacts is 0.073 Ω cm2. With the updated contact resistivities, the theoretical limiting efficiency estimated by Brendel's formulation is therefore 28.5 % for SHJ solar cells, which is comparable to 28.7 % for bi-facial tunneling-oxide passivating contact (TOPCon) solar cells. A hybrid structure consisting of p-type contact from SHJ and n-type contact from TOPCon is feasible to reach 28.9 % limiting efficiency in principle, showing potential of solar cells with hybrid structures.

Simulation approach of new photovoltaic structures based on epitaxial silicon thin layers on a monocrystalline silicon substrate

In the photovoltaic field, research is focused on two important axes: increasing cell efficiency, and reducing fabrication costs. To reduce the cost of the base materials, it is necessary to reduce the thickness of the active layers. The basic idea is to make a layer of high structural and electronic quality silicon of small thickness (10–50 μm). This layer could be grown by epitaxial techniques on a low-cost monocrystalline silicon substrate with an emitter formed by phosphorus diffusion. The silicon layer is characterized by a diffusion length comparable to its thickness, a value that can be expected for the epitaxial layers. This study aims to optimize the physical and technological performances of a crystalline silicon solar cell deposited by an epitaxial process on a low-cost monocrystalline silicon substrate with large thicknesses since there is no reflector on the backside. This structure is characterized by the following parameters: (Thickness of the base layer XB = 56 μm, the efficiency η = 15.2%, the open-circuit voltage Voc = 623 mV and the short-circuit current Isc = 30 mA). The calculations were carried out by the PC1D software, aiming to find a new solar cell structure by keeping the same characteristic parameters mentioned above (η, Isc, and Voc) while decreasing the thickness of this solar cell. The effect of the different parameters on the performance of the solar cell was investigated. The obtained results showed that it is possible to reduce the substrate thickness from 56 to 30 μm while keeping the same characteristics parameters of the cell (η = 15.2%, Voc = 622.7 mV, Isc = 30.1 mA).

Anti-reflection for monocrystalline silicon from diamond-like carbon films deposited by magnetron sputtering

In this work, diamond-like carbon (DLC) films used as anti-reflective coatings for monocrystalline silicon were deposited by magnetron sputtering for potential application in solar cells. The microstructural and optical properties of the films were investigated as a function of substrate temperature over a wide range during deposition. It showed that, when the substrate temperature increased from RT to 800 °C, the hybridized structures of the DLC films accordingly changed associated with a significant variation of refractive index between2.22 and 1.64 at a wavelength of 550 nm. Three types of coating systems, namely single-, three- and five-layer films on monocrystalline silicon substrates, were designed based on the anti-reflection principle and fabricated in terms of the relationships of refractive index and deposition rate with substrate temperature. In particular, a well-designed three-layer film, of which the refractive index gradually changed along the thickness, that is 1.8, 1.9 and 2.0, respectively, was successfully deposited at one step on monocrystalline silicon substrates by adjusting substrate temperature and deposition time, and featured a broadband anti-reflective characteristic with low average reflectivity of 8.7% at a wide solar spectrum of 400–1100 nm. This work demonstrates that the DLC film has a promising application potential as broadband anti-reflective coatings in silicon-based solar cells.