Silicon Technology Research Articles

Two‐Dimensional Heterostructure Complementary Logic Enabled by Optical Writing

Integrated logic circuits using atomically thin, two‐dimensional (2D) materials offer several potential advantages compared to established silicon technologies such as increased transistor density, circuit complexity, and lower energy dissipation leading to scaling benefits. In this article, a novel approach to achieve tunable doping in 2D semiconductors is explored to achieve complementary transistors and logic integration. By selectively transferring WSe2 onto hBN and SiO2 substrates, complementary transistor behavior (n‐ and p‐type) was achieved using a UV light source and electrostatic activation. Furthermore, advanced characterization techniques, including high‐resolution transmission electron microscopy (HRTEM) and Kelvin probe force microscopy (KPFM), provided insights into the chemical composition and surface potential changes after UV writing. Finally, a logic inverter was successfully implemented using selectively photo‐induced doped WSe2 transistors, showcasing the potential for practical logic applications. This innovative method opens new avenues for designing energy‐efficient and reconfigurable 2D semiconductor circuits, addressing key challenges in modern electronics.

SILICON PHOTODIODE FOR TELECOMMUNICATIONS (FSO) WITH INCREASED SPEED AND SENSITIVITY AT 980 nm

One of the basic elements of Free Space Optics is a photodiode, which must have a high level of sensitivity to radiation in the range of 0.8-1 μm, and be fast-acting. In our case, the chosen wavelength is 980 nm, which corresponds to the wavelength of a vertical-cavity surface-emitting laser (VCSEL). The optimization of the photodiode design is carried out taking into account the uniform generation of the photocurrent with a uniform volume charge density inside the crystal when receiving radiation with a working wavelength. The current of the photo signal in the external circuit, in this case, depends on the modulation frequency, the width of the space charge region (SCR), the mobility of minor charge carriers and the amount of bias at the p-n junction. This allows you to significantly manipulate the rise time of the transient characteristic of the photodiode, and the use of double passage of the radiation beam throughout the SCR, you can obtain a significant increase in sensitivity. The subject is the construction of a photodiode, which at a wavelength of 980 nm has small values of the rise time and high values of current monochromatic sensitivity. The goal is to substantiate and create a design of a photodiode with increased current monochromatic sensitivity and reduced rise time at 980 nm wavelengths for operation in FSO. Task: To analyze the factors affecting the sensitivity and rise time of the photodiode when working at a wavelength of 980 nm, as well as to develop the design of the photodiode and investigate it. Methods: mathematical analysis of photoelectric parameters of a photodiode taking into account the mechanism of generation of minor charge carriers. Modeling of the photodiode design. A planar technology for silicon was used to manufacture the photodiode. The technical solution is based on the optimization of the modulation frequency, the width of the SCR, the mobility of minor charge carriers and the amount of displacement at the p-n junction, as well as ensuring the double passage of radiation through the photodiode crystal. The result was also achieved by etching the mesastructure from the reverse side of the photodiode, the area of which is the projection of the photosensitive element of the photodiode, and the width of the silicon plate above the mesastructure should be about 50 μm. Results: Factors affecting the current monochromatic sensitivity of the photodiode and its rise time were determined and taken into account. A new photodiode design with increased sensitivity and reduced rise time has been created. Comparative studies of the manufactured batch of created photodiodes and FD-255A photodiodes were conducted, which showed that the proposed photodiode really has a current monochromatic sensitivity at a wavelength of 980 nm of at least 0.55 A/W. At the same time, its rise time was reduced from 50 ns to 20 ns. compared to the serial photodiode FD-255A.

A metaheuristic-based method for photovoltaic temperature computation under tropical conditions

Tropical climates have favorable irradiation levels for the development of photovoltaic systems; however, high temperatures have a negative impact on the efficiency of solar cells. Since direct measurement of cell temperature is not common, mathematical models are needed to make predictions. Numerous models have been documented, highlighting the challenge of applying a universal model to different climatic conditions. The main contribution of this study is the proposal of a metaheuristic algorithm to accurately compute the temperature of solar cells. This method is simple and effective in exploring numerous potential states of the reference parameters (i.e., irradiance and ambient temperature). Data collected over a 23-month period in two photovoltaic installations with an output power of 2.2 MW of multicrystalline silicon technology were used to develop the proposed method and validate it. The proposed model was compared with 19 previously reported models in the literature. Compared to the model recommended by the International Electrotechnical Commission (IEC Standard 61215-1), the mean square error, mean absolute error (MAE) and mean absolute percentage error were reduced by 4.9, 4.8, and 2.4 times, respectively. The accuracy of the proposed method is demonstrated by MAE errors ranging from 0.56 °C to 1.88 °C, obtained by considering three different daily profiles of irradiance and ambient temperature. Therefore, the proposed method is recommended to more accurately calculate the temperature of the photovoltaic cell in tropical areas.

Experimental CIGS technology performance under low concentration photovoltaic conditions

This research study assesses the influence of the concentration factor on two different PV technologies: c-Si and CIGS, to analyze the feasibility of utilizing CIGS thin-film technology in Low Concentration Photovoltaic conditions. Additionally, the importance of the encapsulation design is explored to determine the optimum thermal management strategy. The initial phase involves an analysis of the thermal performance of two types of commercial photovoltaic module and explores the enhancement of temperature management in CIGS photovoltaics modules by substituting the rear glass backsheet with an aluminum sheet to reduce the operating temperature of the prototype. Subsequently, various prototypes are fabricated, incorporating CIGS and silicon technologies, and different encapsulation designs: tedlar, glass and aluminum backsheets. The analysis reveals that comparing performance under 2.2× and 1× concentration conditions, CIGS technology exhibits the higher performance at 2.2×, making it a more promising choice for LCPV systems. While CIGS technology boasts an intrinsic advantage because of its open circuit voltage temperature coefficient, its performance enhancement under LCPV conditions is further amplified through the optimization of the backsheet to improve the thermal management.

Дослідження розподілу кисню по довжині монокристалів кремнію, легованих компонентами з різним типом провідності

The purpose of the article is the study of convective flows and their influence on the growth of single crystals of silicon by the Czochralsky method from a large melt, which contributes to the emergence of non-stationary convection. Therefore, simulation of convection for the growth of silicon single crystals is an important step in the development of conditions for the growth of perfect single crystals. Silicon substrates are used to manufacture more than 90% of semiconductor devices and solar cells. A special role in the development of electronics is played by monocrystalline silicon, which is used for the manufacture of semiconductor devices and integrated microcircuits. The main requirements for the development of technology for the production of silicon substrates is an increase in quality at a decrease in cost. Promising technologies of 10-nm size and 3D-transistor structures significantly increase the requirements for uniformity of distribution of components, including layering in silicon single crystals. For the mathematical modeling of convective flows, melt flows were considered for a cylindrical crucible with a radius of 150 mm at a melt height of up to 40 mm. Such parameters ensure stationary convection in molten silicon. Methods of reducing stratification have been studied and developed for more than 50 years, but have not yet found a definitive solution. This method of single crystal growth is the most controlled and allows to influence the convective flows in the silicon melt below the phase interface with ultrasonic waves in the megahertz range. The effectiveness of using ultrasound in the extraction of semiconductor single crystals depends on the creation of special conditions for introducing them into the melt. 
 Reducing the influence of oxygen on the electrophysical properties of silicon single crystals is an intractable problem of silicon technology. One of the ways to solve this problem is alloying with an isomorphic impurity, for example, tin. The development of a method of doping single crystals of silicon with tin requires determination of its concentration in the liquid and solid phases

Integration of epitaxial LiNbO3 thin films with silicon technology

Development of bulk acoustic wave filters with ultra-wide pass bands and operating at high frequencies for 5th and 6th generation telecommunication applications and micro-scale actuators, energy harvesters and sensors requires lead-free piezoelectric thin films with high electromechanical coupling and compatible with Si technology. In this paper, the epitaxial growth of 36°Y-X and 30°X-Y LiNbO3 films by direct liquid injection chemical vapour deposition on Si substrates by using epitaxial SrTiO3 layers, grown by molecular beam epitaxy, has been demonstrated. The stability of the interfaces and chemical interactions between SrTiO3, LiNbO3 and Si were studied experimentally and by thermodynamical calculations. The experimental conditions for pure 36°Y-X orientation growth have been optimized. The piezoelectricity of epitaxial 36°Y-X LiNbO3/SrTiO3/Si films was confirmed by means of piezoelectric force microscopy measurements and the ferroelectric domain inversion was attained at 85 kV.cm−1 as expected for the nearly stoichiometric LiNbO3. According to the theoretical calculations, 36°Y-X LiNbO3 films on Si could offer an electromechanical coupling of 24.4% for thickness extension excitation of bulk acoustic waves and a comparable figure of merit of actuators and vibrational energy harvesters to that of standard PbZr1−x Ti x O3 films.

High‐Frequency fT and fmax in Organic Transistors: Performance and Perspective

AbstractIn state‐of‐the‐art organic transistors, the transit frequency fT is reported to be fT = 40 MHz for vertical organic transistors, where a voltage‐normalized fT corresponds to 0.36 MHz V−2. The reported highest fT for conventional organic transistors is fT = 160 MHz, where the voltage‐normalized fT is 0.1 MHz V−2. While the reported transit frequency fT of n‐MOSFETs for silicon technology when normalized by the applied biases exceeds 300 GHz V−2. The reported carrier mobility of organic semiconductors is over 100 cm2 V−1 s−1, which is almost an order of magnitude lower than that of silicon. However, the transit frequency fT of organic transistors lags far behind silicon technology by about six orders of magnitude at a comparable device length below 300 nm. In this work, a technology computer‐aided design (TCAD) simulator is adjusted to the experimental DC and AC characteristics of the 200 nm device length vertical organic permeable‐base transistors (OPBTs) based on C60 as semiconductor. The AC performance of the devices is investigated and quantitatively analyzed the influence and contribution of key design, structure and material parameters that determine fT and fmax. The feasible ways to enhance and optimize the highest achievable fT and fmax are identified to reach the and overcome the limitations to high‐frequency operation in organic transistors.

A new energetic scenario with renewable energy

The article presents a summary of the new energy scenario, based on distributed generation and on the integration into the electricity networks of the generators of small and medium power. They are based on clean technologies and renewable energy, including cogeneration, micro-generation with renewables (non-fossil energy sources, such as wind, solar, geothermal, tidal, hydroelectric, biomass), energy storage systems, energy efficiency techniques, and flexibility and demand responsibility techniques. The perspective shows a new system, where thousands or millions of users are their own generators, becoming producers and consumers of electricity. All these generators will be interconnected through an electricity network totally interactive and intelligent. For this new environment a sophisticated control and communications technologies are required to ensure the correct operation of the electricity networks, the creation of new models of power distribution, and advanced technology development of energy storage, power electronics and superconductor devices. The main technology that can lead to this new revolution, equivalent to the technology of silicon, which is revolutionizing the conventional limits of electricity and electronics, is nanotechnology, as well as its applications in the development of new nanostructured materials. The new energy systems will present smaller scale, will be easier to build and dismantle, decentralized, renewable, with localized and decentralized energy production.

Tuning the Physically Induced Crystallinity of Microfabricated Bioresorbable Guides for Insertion of Flexible Neural Implants

AbstractDevices that safely interface with the brain are critical to advancing neuroengineering. Thin and flexible neural implants show great promise alongside established silicon technologies. They therefore require a physical stiffener to allow their insertion into brain tissue. Bioresorbable polymer shanks are novel transient guides enabling accurate implantation using biocompatible materials that will be absorbed by the body over time. The development of materials with optimized stiffness and degradation is needed to provide minimally invasive probes with precise insertion capability under surgical conditions. A microfabrication protocol for the patterning of polyvinyl alcohol and its physical cross‐linking is presented, resulting in insertion guides with precise shapes and tunable degradation and stiffness. The results demonstrate a remarkable improvement in batch fabricating micro‐scale neural shanks with designed crystallinity. It results in their prolonged degradation time, evaluated in agarose gel, and remarkably improved penetrability due to the increase in mechanical stiffness. In vitro and in vivo studies support the high acceptability of this combination in interfacing with neural cells and tissue. This work represents a novel approach to the material and process engineering of bioresorbable polymers for developing fully organic and safe implants.

Parity-conserving Cooper-pair transport and ideal superconducting diode in planar germanium

Superconductor/semiconductor hybrid devices have attracted increasing interest in the past years. Superconducting electronics aims to complement semiconductor technology, while hybrid architectures are at the forefront of new ideas such as topological superconductivity and protected qubits. In this work, we engineer the induced superconductivity in two-dimensional germanium hole gas by varying the distance between the quantum well and the aluminum. We demonstrate a hard superconducting gap and realize an electrically and flux tunable superconducting diode using a superconducting quantum interference device (SQUID). This allows to tune the current phase relation (CPR), to a regime where single Cooper pair tunneling is suppressed, creating a sin left(2varphi right) CPR. Shapiro experiments complement this interpretation and the microwave drive allows to create a diode with ≈ 100% efficiency. The reported results open up the path towards integration of spin qubit devices, microwave resonators and (protected) superconducting qubits on the same silicon technology compatible platform.

Nanomaterial-Based Artificial Vision Systems: From Bioinspired Electronic Eyes to In-Sensor Processing Devices.

High-performance robotic vision empowers mobile and humanoid robots to detect and identify their surrounding objects efficiently, which enables them to cooperate with humans and assist human activities. For error-free execution of these robots' tasks, efficient imaging and data processing capabilities are essential, even under diverse and complex environments. However, conventional technologies fall short of meeting the high-standard requirements of robotic vision under such circumstances. Here, we discuss recent progress in artificial vision systems with high-performance imaging and data processing capabilities enabled by distinctive electrical, optical, and mechanical characteristics of nanomaterials surpassing the limitations of traditional silicon technologies. In particular, we focus on nanomaterial-based electronic eyes and in-sensor processing devices inspired by biological eyes and animal visual recognition systems, respectively. We provide perspectives on key nanomaterials, device components, and their functionalities, as well as explain the remaining challenges and future prospects of the artificial vision systems.

Unravelling the nanoscale mechanism of polarization reversal in a Hf0.5Zr0.5O2-based ferroelectric capacitor by vector piezoresponse force microscopy.

Ferroelectricity is in demand in many device concepts in electronics, energy and microsystem engineering. The performance of ferroelectrics-based devices is determined by either out-of-plane or in-plane polarization, or out-of-plane or in-plane piezoelectric strain. Real prospects for the practical implementation of innovative devices opened up after the discovery of ferroelectricity in ultrathin hafnium oxide films, due to their perfect compatibility with silicon technology. Ferroelectric properties of this material have been assigned to an orthorhombic structural phase with a single polar axis, but the spatial orientation of the polarization vector and the tensorial piezoelectric behaviour, which are inextricably coupled, still remain unknown. Herein, the rotation of the polarization vector in a Hf0.5Zr0.5O2 (10 nm) capacitor during polarization switching and the spatial distribution of longitudinal and shear piezoelectric coefficients are elucidated at the nanoscale using operando vector piezoresponse force microscopy. In most of the capacitor, a 180°-flipping of the polarization vector is observed, which is consistent with the orthorhombic phase structure. However, a rather large fraction of the capacitor is also occupied by nanoregions of ferroelastic (non-180°) switching, which is explained by the effect of the local mechanical stress. To quantify the three-dimensional piezoresponse, a novel approach exploiting the Poisson effect in artificially created non-ferroelectric regions is proposed and it shows that the shear piezoelectric coefficient is twice the longitudinal coefficient. The experimental insights entail an important step in fundamental understanding of the ferroelectric and piezoelectric properties of hafnium oxide and have great potential to trigger new versions of ferroelectric-based devices.

Selective growth of vanadium dioxide on patterned Al/SiO2 substrates by metal–organic chemical vapor deposition

The area-selective growth of vanadium dioxide can provide a valuable self-aligned process promising for novel oxide electronics compatible with silicon technology.

Search for toroids in excited nuclear material

Ground state nuclei usually have compact geometries. However, there have been theoretical predictions that excited nuclei can take on more extended shapes such as toroids or bubbles. There have been many attempts to identify signatures of such shapes in experimental data. One signature, both predicted by theory and reported in experimental data, is narrow resonances at high excitation energy in peripheral intermediate-energy heavy-ion collisions. This potential evidence for toroidal states was reported in the alpha particle disassembly of 28Si after collision with a 12C target at 35 MeV/nucleon. The prior work was limited by angular resolution and statistical uncertainties. The present work aims to measure the excitation energy distribution for these disassembly events with improved angular resolution and reduced statistical uncertainty using the Forward Array Using Silicon Technology (FAUST). FAUST is equipped with resistive dual-axis duo-lateral (DADL) position-sensitive silicon detectors capable of sub-millimeter position resolution. The measured excitation energy distributions of 7-α disassembly events showed no strong evidence for highly excited states at the cross section and widths suggested by previous experiment.

The contradiction between thermodynamic and kinetic effects of stress-modulated antiferroelectricity in ZrO2 thin films.

The discovery of antiferroelectricity in fluorite-structured binary oxides has opened up promising directions for next-generation electronic devices due to their excellent scalability and compatibility with silicon technology. However, understanding and improving the antiferroelectricity remain ambiguous and present considerable challenges for device applications. In this work, we discover a contradiction between the thermodynamic and kinetic effects of stress-modulated antiferroelectricity in ZrO2 thin films. On the one hand, we observe a monotonically enhanced antiferroelectricity in a ZrO2 thin film grown on the bottom electrode with a reduced coefficient of thermal expansion, i.e., ranging from Ni to TiN and W. The combined experimental characterizations and first-principle calculations show that the out-of-plane compressive stress induced by the electrode promotes the formation of the tetragonal phase, producing enhanced antiferroelectricity. On the other hand, the out-of-plane compressive stress increases the energy barrier between the tetragonal and polar orthorhombic phases, hindering the reversible phase transition between them. As a result, the antiferroelectricity of the samples annealed with top electrodes is worse compared to those without top electrodes. Our findings not only deepen the understanding of antiferroelectricity in ZrO2 thin films but also provide a strategy for improvement.

Life cycle assessment of an innovative high-value-recovery crystalline silicon photovoltaic recycling process − the environmental impacts and benefits

A universal high-value-recovery recycling technology for crystalline silicon (c-Si) photovoltaic (PV) modules developed by the French company ROSI is presented in this study. The maturity of the technology reaches TRL 8 and has been deployed in an industrial site. The environmental impact of the recycling process is evaluated by performing a life cycle assessment (LCA), with calculations based on the default life cycle impact assessment method as recommended by the Environmental Footprint methodology. Hotspots are identified and measures for future process optimization are proposed. Furthermore, the potential environmental benefits brought by the high-quality secondary raw materials are evaluated by applying system expansion in the LCA. The results show that ROSI recycling process brings significant environmental benefits in all chosen impact categories, 9 out of 14 impact categories show 90% impact savings compared to conventional production activities. This study complements the lacking LCA information at the end-of-life (EoL) stage of PV's life cycle, especially those of advanced recycling technologies other than landfilling or shredding and highlights the advantage of high-value recovery technology. Future works on LCA are also proposed for further precise assessment. Finally, this study concludes the implication of applying a high-value-recovery recycling technology from a supply chain perspective.

Innovative and sustainable solar cells based on abundant elements on the Earth crust

Antimony selenide is a very promising material for photovoltaic applications, with the potential to become a competitive alternative to more traditional silicon, CdTe and CIGS-based technologies. A notable feature of Sb2Se3 is its strong anisotropy, and this property is reflected in the performance parameters of the solar cell. In this study a novel method is explored to control the grain orientation and its effects on the photovoltaic parameters of the solar cells. Furthermore, an innovative approach to create a low-resistivity, Ohmic back-contact is presented, which is crucial for enhancing the efficiency and performance of Sb2Se3-based solar cells.

An organic brain-inspired platform with neurotransmitter closed-loop control, actuation and reinforcement learning.

Organic neuromorphic platforms have recently received growing interest for the implementation and integration of artificial and hybrid neuronal networks. Here, achieving closed-loop and learning/training processes as in the human brain is still a major challenge especially exploiting time-dependent biosignalling such as neurotransmitter release. Here, we present an integrated organic platform capable of cooperating with standard silicon technologies, to achieve brain-inspired computing via adaptive synaptic potentiation and depression, in a closed-loop fashion. The microfabricated platform could be interfaced and control a robotic hand which ultimately was able to learn the grasping of differently sized objects, autonomously.

Modelling recycling for the life cycle assessment of perovskite/silicon tandem modules

With the massive growth of the global capacity of photovoltaics (PV) over the last decade, the PV waste is expected to increase dramatically in the near future. Having potential to reduce the use of raw materials and preserve natural resources, PV recycling is attracting more and more attention. This being said, the environmental impacts over the life cycle of PV technologies, including the end-of-life (EoL) stage, should be evaluated carefully. Life cycle assessment (LCA) is currently the most common methodology to assess the potential environmental impacts of a product throughout its entire life cycle. However, the modelling of recycling in LCA has always been a challenge and no consensus has yet been reached, since the treatment of recycling does not only involve an EoL management of waste, but also the production of recycled material. Perovskite on silicon tandem is a widely investigated emerging PV technology having the potential to overcome the power conversion efficiency (PCE) limit of the single-junction crystalline silicon technology. The EoL modelling seems more challenging in the case of emerging technologies for which the EoL is more uncertain than for established technologies. In this article, six common and important approaches of EoL modelling in LCA were applied to future perovskite/silicon tandem modules to analyze the effect of the different EoL modelling approaches on the LCA results. The aim was to identify the most suitable methodological approaches to account for recycling, when modelling the life cycle of PV modules. The environmental performance of perovskite/silicon tandem modules was assessed over their life cycle and expressed in terms of impacts per m2 of module. After testing the six EoL modelling approaches and comparing the LCA results, the EoL modelling choice was found to lead to non-negligible differences. For example, in terms of climate change, the impact of the tandem modules ranges from 45 to 59 kg CO2-eq/m2. Among the six EoL modelling options, the approaches of simple cut-off and cut-off with economic allocation are more oriented towards the promotion of high rates of recycled material integrated as an input to the assessed product among industrial actors, while the approach of closed-loop allocation provides incentives to maximize the ratio of recycling at the EoL, regardless the initial ratio of recycled content within the product. Some approaches such as the circular footprint formula (CFF) tend to provide both incentives to increase the content of recycled input material in the manufacturing of the product and the recycling ratio at the EoL of such product. After applying the different alternatives, a set of recommendations to select the relevant EoL modelling approaches are provided: 1) the CFF is recommended as a representative approach due to its wide applicability, tending to provide an intermediate result and reflecting the characteristics of materials; 2) sensitivity analysis should be applied to check the robustness of the results, 3) the cut-off approach and the closed-loop allocation should be used at least for the sensitivity analysis.

Potential-induced degradation phenomena in single-encapsulation crystalline Si photovoltaic modules

This paper particularly explains potential-induced degradation (PID) of wafer-based standard p-type crystalline silicon technology. We present a single-encapsulation method that is useful for simulating PID in the laboratory to facilitate microanalyses of module-level solar cells. The PID testing is performed for the module with single-encapsulation and conventional modules. Their current–voltage characteristics and electroluminescence images are investigated before and after the PID tests. As described herein, we infer that the single-encapsulation modules generate PID almost in the same way as conventional modules do, and that the degradation trend is almost identical to that of conventional modules. Results of PID recovery tests indicate that the time necessary for PID recovery is always less than that for PID generation, irrespective of the encapsulation method.