Vanadium dioxide (VO2) stands out for its versatility in numerous applications, thanks to its unique reversible insulator-to-metal phase transition. This transition can be initiated by various stimuli, leading to significant alterations in the material’s characteristics, including its resistivity and optical properties. As the interest in the material is growing year by year, the purpose of this review is to explore the trends and current state of progress on some of the applications proposed for VO2 in the field of sensors and actuators using literature review methods. Some key applications identified are resistive sensors such as strain, temperature, light, gas concentration, and thermal fluid flow sensors for microfluidics and mechanical microactuators. Several critical challenges have been recognized in the field, including the expanded investigation of VO2-based applications across multiple domains, exploring various methods to enhance device performance such as modifying the phase transition temperature, advancing the fabrication techniques for VO2 structures, and developing innovative modelling approaches. Current research in the field shows a variety of different sensors, actuators, and material combinations, leading to different sensor and actuator performance input ranges and output sensitivities.

This article investigates resistive random access memory (ReRAM) crossbar memory arrays, which is a notable development in non-volatile memory technology. We highlight ReRAM’s competitive edge over NAND, NOR Flash, and phase-change memory (PCM), particularly in terms of endurance, speed, and energy efficiency. This paper focuses on the architecture of crossbar arrays, where memristive devices are positioned at intersecting metal wires. We emphasize the unique resistive switching mechanisms of memristors and the challenges of sneak path currents and delve into the roles and configurations of selectors, particularly focusing on the one-selector one-resistor (1S1R) architecture with an insulator–metal transition (IMT) based selector. We use SPICE simulations based on defined models to examine a 3 × 3 1S1R ReRAM array with vanadium dioxide selectors and titanium dioxide film memristors, assessing the impact of ambient temperature and critical IMT temperatures on array performance. We highlight the operational regions of low resistive state (LRS) and high resistive state (HRS), providing insights into the electrical behavior of these components under various conditions. Lastly, we demonstrate the impact of selector presence on sneak path currents. This research contributes to the overall understanding of ReRAM crossbar arrays integrated with IMT material-based selectors.

This paper presents a new open-source simulator that aims to provide a tool to study a wide range of current and future problems requiring high-resolution distributed simula tion in engineering practice, especially in microelectronics. The problem to be studied is defined as a circuit model, which can be specified by a SPICE-like description. The simulator solves this circuit using the highly efficient Successive Network Reduction Method, optimized specifically for solving circuit models of fields discretized by the Finite Differences or Finite Volumes methods. The circuits can be extended with programmable special components: controllers, to easily implement special tasks such as hysteresis or ray tracing modelling.

A New SPICE model for insulator-metal transition (IMT) devices is presented in this paper. The combined influences of the electric field and Joule heating are considered, allowing a transition from the high-resistance monoclinic phase to the low-resistance metallic one. Hysteresis, observed in specific IMT materials such as vanadium dioxide, is effectively addressed. The model's accuracy was validated using experimental results and electro-thermal FVM simulations. It has been implemented in VHDL-AMS, ensuring its compatibility with SPICE simulators like Xpedition AMS and PartQuest Explore, which were employed in this research. The model characterizes three specific device states, heating, cooling, and equilibrium. Transition dynamics between these states are tied to historical temperature data, represented as the device's temperature time derivative. To our knowledge, this model is the first IMT compact model that addresses hysteresis and is the first VHDL-AMS for IMT devices. With this development, circuit designers are provided with tools to fully explore the potential of VO 2 and similar IMT devices to design and realize next-generation electrical circuits.

Thermal sensors are widely used in different areas such as, automotive, defense, healthcare, and fire protection. Heat management is a hot topic nowadays, especially in electronics and power electronic packages, due to the miniaturization of semiconductor devices dimensions. New materials and concepts are studied to develop thermal sensors with more excellent reliability and sensitivity. Vanadium dioxide is a strongly correlated electron material with interesting thermal and optical properties due to its transition from a low-conducting phase to a high-conducting phase called metal-to-insulator transition. This study investigates two different models to use vanadium dioxide as a sensing element by presenting simulations performed on SUNRED simulator.

Due to reaching the end of Moore’s era and minimising CMOS technology becomes difficult. Finding different materials to keep electronic devices evolving is a matter of scientists. A thermal electronic logic circuit (TELC) is one of the most prominent alternatives that has been proposed recently. Vanadium dioxide (VO 2 ) is an essential material that has been utilised in TELC due to its thermal and electrical properties. VO 2 transits its electrical property from the semiconductor phase into the metal phase at around 67°C. In this paper, two numerical methods were used to determine the electrical and thermal characteristics of VO 2 , and measured data compared the results. The phase-change material behaviour was modelled by two different softwares using different simulation methods, finite volume method FVM and finite element method FEM. The sample preparation and the thermal and electrical measurements were carried out in our cleanroom.

Thanks to the System-on-Package technology (SoP) the integration of different elements into a single package was enabled. However, from the thermal point of view the heat removal path in modern packaging technologies (FCBGA) goes through several layers of thermal interface material (TIM) that together with the package material create a relatively high thermal resistance which may lead to elevated chip temperature which causes functional error or other malfunctions. In our concept, we overcome this problem by creating integrated microfluidic channel based heat sink structures that can be used for cooling the high heat dissipation semiconductor devices (e.g.: processors, high power transistor or concentrated solar cells). These microchannel cooling assemblies can be integrated into the backside of the substrate of the semiconductor devices or into the system assemblies in SoP technology. In addition to the realization of the novel CMOS compatible microscale cooling device we have developed precise and valid measurement methodology, simulation cases studies and a unique compact model that can be added to numerical simulators as an external node. In this paper the achievements of a larger research are summarized as it required the cooperation of several experts in their fields to fulfil the goal of creating a state-of-the-art demonstrator. Thanks to the System-on-Package technology (SoP) the integration of different elements into a single package was enabled. However, from the thermal point of view the heat removal path in modern packaging technologies (FCBGA) goes through several layers of thermal interface material (TIM) that together with the package material create a relatively high thermal resistance which may lead to elevated chip temperature which causes functional error or other malfunctions. In our concept, we overcome this problem by creating integrated microfluidic channel based heat sink structures that can be used for cooling the high heat dissipation semiconductor devices (e.g.: processors, high power transistor or concentrated solar cells). These microchannel cooling assemblies can be integrated into the backside of the substrate of the semiconductor devices or into the system assemblies in SoP technology. In addition to the realization of the novel CMOS compatible microscale cooling device we have developed precise and valid measurement methodology, simulation cases studies and a unique compact model that can be added to numerical simulators as an external node. In this paper the achievements of a larger research are summarized as it required the cooperation of several experts in their fields to fulfil the goal of creating a state-of-the-art demonstrator.

Large area multi-chip LED devices, such as chip-on-board (CoB) LEDs, require the combined use of chip-level multi-domain compact LED models (Spice-like compact models) and the proper description of distributed nature of the thermal environment (the CoB substrate and phosphor) of the LED chips. In this paper, we describe such a new numerical solver that was specifically developed for this purpose. For chip-level, the multi-domain compact modeling approach of the Delphi4LED project is used. This chip-level model is coupled to a finite difference scheme based numerical solver that is used to simulate the thermal phenomena in the substrate and in the phosphor (heat transfer and heat generation). Besides solving the 3D heat-conduction problem, this new numerical simulator also tracks the propagation and absorption of the blue light emitted by the LED chips, as well as the propagation and absorption of the longer wavelength light that is converted by the phosphor from blue. Heat generation in the phosphor, due to conversion loss (Stokes shift), is also modeled. To validate our proposed multi-domain model of the phosphor, dedicated phosphor and LED package samples with known resin-phosphor powder ratios and known geometry were created. These samples were partly used to identify the nature of the temperature dependence of phosphor-conversion efficiency and were also used as simple test cases to "calibrate" and test the new numerical solver. With the models developed, combined simulation of the LED chip and the CoB substrate + phosphor for a known CoB LED device is shown, and the simulation results are compared to measurement results.

Emerging devices and materials in computing industry are recently of great interest because classical silicon-based circuit development is saturating due to scaling limits. Thermal-electronic logic circuit (TELC) concept is a promising approach to enhance conventional CMOS circuits or even replace them. Semiconductor-to-metal transition (SMT) of vanadium dioxide (VO 2 ) is the main part of TELC as it allows transmission and control of information flow both electrically and thermally. The first TELC inverter is introduced in this article, dynamic simulations are performed to test its behavior and relation between propagation delay and input voltage is demonstrated. A new phase transition model is used to upgrade our SUNRED simulator. This new version is accurate and proved to be suitable for dynamic simulations. This article presents first dynamic simulation of SMT material.

Advancement of classical silicon-based circuit technology is approaching maturity and saturation. The worldwide research is now focusing wide range of potential technologies for the “More than Moore” era. One of these technologies is thermal-electronic logic circuits based on the semiconductor-to-metal phase transition of vanadium dioxide, a possible future logic circuits to replace the conventional circuits. In thermal-electronic circuits, information flows in a combination of thermal and electronic signals. Design of these circuits will be possible once appropriate device models become available. Characteristics of vanadium dioxide are under research by preparing structures in laboratory and their validation by simulation models. Modeling and simulation of these devices is challenging due to several nonlinearities, discussed in this article. Introduction of custom finite volumes method simulator has however improved handling of special properties of vanadium dioxide. This paper presents modeling and electro-thermal simulation of vertically structured devices of different dimensions, 10 nm to 300 nm layer thicknesses and 200 nm to 30 μm radii. Results of this research will facilitate determination of sample sizes in the next phase of device modeling.

The multi-domain operation of blue pump LEDs in a chip-on-board (CoB) device cannot be described properly by the existing chip level multi-domain compact models and a package compact thermal model because their operation is strongly affected by such parts of the environment as the substrate or the phosphor. In this case a mix of compact modelling and distributed modelling approaches need to be used. This paper presents a method that applies a chip level multi-domain LED compact model in a distributed way for the simulation of the LED chips and a Finite Volume Method based description for the whole package, including the temperature dependent light conversion taking place in the phosphor layer covering the entire LED chip array. The chip model describes the electrical, thermal and light output characteristics and their mutual dependence. This paper presents a new multi-domain phosphor model based on path tracing algorithms to describe the blue-to-yellow conversion, heat loss and light propagation in a distributed way for white CoB LEDs.

In a recent European H2020 project on LED characterisation and modelling (Delphi4LED, www.delphi4LED.eu)the major target was to represent physical LED package types by their digital twins in form of multi-domain compact models.In this project a specific task was devoted to CoB LEDs.Phosphor converted white CoB LEDs are large area devices on a ceramic substrate of high thermal conductivity, with a few dozens of LED chips mounted, covered by a phosphor layer.Such devices represent real technical challenges both in terms of their physical measurement and modelling.In this paper we report on our work regarding measurement and modelling of such devices performed in the context of the aforementioned project.

Thermal-electrical logic circuits can be a possible alternative to CMOS technology. The basic element of these circuits is the vanadium dioxide resistor. Currently, only macroscopic models exist for the operation of VO2 resistors. The development of a submicron model requires the design, production and measurement of submicron-sized samples. In this paper, high-resolution electro-thermal VO2 resistor simulations are performed using a macroscopic material model in the range of 200 μm to 50 nm resistor width and 20 μm to 50 nm length with 50 nm layer thickness. These results in the submicron range can only be considered as estimates, but they can be used to determine the size of the samples required for submicron modelling.

In this paper an extension of SYSRED (SYstem function Successive network REDuction) simulation tool is presented to handle the heat generated in the phosphor layer of a phosphor converted white LED device. The heating effect of light conversion and the attenuation of light flux is taken into account through a resistance network between the source (LED chip) and the active converting nodes. With this tool, the transfer function network for the lens of a Cree XP-E LED device is created and reduced so as to connect it to a similarly reduced LED model. The results from the reduced order model show a good agreement compared to measurement data obtained for devices examined in the Delphi4LED project.

Besides classical inorganic LEDs, intelligent light sources can be also based on organic LEDs. OLEDs function as surface light sources and manufacturing of large area light sources is feasible with OLED technologies. Despite their lower luminous efficacy their other properties make OLEDs still an attractive option especially in high end indoor applications. In natural convection environment the temperature difference in the same OLED panel can reach 20-30 degrees C which can result in up to 30-40% difference in current density and thus, in the luminance. This difference in temperature and current density leads to differential ageing of the organic materials. CFD simulation is the obvious way to investigate natural convection environments but integration of a CFD solver in an OLED simulator may be difficult and the solution times are high. As a possible workaround to this problem, in this paper the application of five natural convection models for vertical plates in an electro-thermal field solver based OLED simulator as thermal boundary condition are presented. Steady state and transient simulation results of a free-standing 50 x 50 mm(2) active surface OLED, surrounded by still air, are compared with measurement results. A typical failure type of OLED5 is thermal runaway caused by e.g. manufacturing problems, operational damages or overcurrent. The paper presents the effect of the natural convection model on the overcurrent caused thermal runaway simulation results.

In this paper, a novel tool and a methodology are introduced to create a thermally driven digital cell placement capability that considers the cooling capability of the integrated microscale heatsink structures. Normally, the realization of this kind of placement would require time-consuming computation fluid dynamics (CFD) simulations. With the presented solution, the CFD tool can be replaced by a thermal simulator, which incorporates analytical fluid dynamics compact models. By this approach, the determination of the precise local heat transfer coefficient(s) (thus cooling efficiency) can be realized. In addition, the temperature distribution along the microchannels can also be obtained depending on the channel geometries, the thermal properties of the fluid and the wall temperature(s). While this model is integrated into the thermal simulator, it is still needed to be connected to commercial digital IC design tools to unleash its full potential. Therefore, the interfacing tool is also developed that launches either the thermal, the electrical, or logical simulators and placement programs by using the outputs (results) of the other programs as the inputs.

Organic LEDs can be used not only in displays but also in intelligent light sources. Unlike inorganic LEDs, OLEDs do not function as point-like but as surface light sources since manufacturing of large area light sources is more feasible with OLED technologies. Despite their lower luminous efficacy this makes OLEDs still an attractive option especially in high end indoor applications, The major issue in such applications is the homegenity of the luminance of the large OLED panels. In natural convection environment the temperature difference in the same device can reach 20-30°C which can result in up to 30-40% difference in current density and thus in the luminance. CFD simulation is the obvious way to handle this problem but integration of a CFD solver in an OLED simulator may be difficult and the solution times are high. This paper presents the application of three natural convection models for vertical plates in an electro-thermal field solver based OLED simulator as thermal boundary condition. Simulation results of a free-standing 50×50 mm 2 active surface OLED, surrounded by still air, are compared with measurement results.

Limits of development of conventional silicon-based integrated circuits get closer. More and more effort is done to develop new devices for integrated circuits. A promising structure is based on the semiconductor-to-metal phase change of vanadium-dioxide at about 67°C. In these circuits the information is carried by combined thermal and electrical currents. For device modelling and circuit design, accurate distributed electro-thermal transient simulation is mandatory. This paper is the first one to present an electro-thermal transient simulation method for VO2 devices operating in real-world conditions. The paper presents three VO2 material models, the algorithmic extension of an electro-thermal field simulator to be able to handle hysteresis and the transient simulation issues of VO2 and the modelling of VO2 based devices. The paper compares measured and simulated device characteristics.

New active thermal-electronic device family is proposed. These devices operate by means of thermal (or hot electron) coupling between adjacent domains containing heating (input) and thermally sensitive (output) elements. The theoretical background, basic equations and comparison with the conventional electron devices are the main subject of this work. According to the theoretical assumptions the realization of the thermal-electronic device needs a very sensitive output element i.e. temperature sensor. Among others, the metal-insulator transition (MIT) based resistor fulfills this requirement. The MIT resistor itself has got thyristor-like I-V characteristics due to solely the high electric field, or Joule heating induced extremely strong step-like resistance drop at a given temperature. Using thermally coupled MIT and/or other resistors it is possible to build a special device, namely phonsistor (=phonon transistor). This device consists of only bulk type intrinsic domains, containing significantly fewer regions, junctions, depleted layers, surfaces and interfaces compared to conventional electron devices. Thus, these devices can be integrated together with each other and with conventional CMOS, forming, for example, thermal-electronic logic circuit (TELC) for the More-Than-Moore concept devices. (C) 2017 Elsevier B.V. All rights reserved.

In this article a new methodology is introduced to create a ladder-type analytical thermal model for microscale channel based heatsink structures. The presented model is applicable to determine the local heat transfer(s) and the temperature distribution along the channel depending on the channel geometries, the thermal properties of the fluid and the wall temperature(s). The channel is divided into several segments and for each segment a T-equivalent circuit is created. The ladder-type thermal model obtained by applying the T-equivalent subcircuit as a building block can be used as a compact model of microscale channel structures. This model was implemented in a conventional thermal field solver (CTFS) simulation tool to augment the capability of simulating the thermal impact of integrated heat sink structures even with radial channel pattern. The implementation steps and the results are compared to the analytically calculated, CFD modelled and measured values. This augmented CTFS engine gives the opportunity to investigate the operation of system-on-package devices by electro/logi-thermal simulation.