Toomas Rang

Toomas Rang
Tallinn University of Technology | TTU · Thomas Johann Seebeck Department of Electronics

PhD

About

126
Publications
17,687
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226
Citations

Publications

Publications (126)
Article
Full-text available
Recently, quantum-dot-based core/shell structures have gained significance due to their optical, optoelectronic, and magnetic attributes. Controlling the fluorescence lifetime of QDs shells is imperative for various applications, including light-emitting diodes and single-photon sources. In this work, novel Cu-doped CdS/ZnS shell structures were de...
Article
Full-text available
This paper proposes a deep Reinforcement Learning (RL) based co-design approach for joint-optimization of wireless networked control systems (WNCS) where the co-design approach can help achieve optimal control performance under network uncertainties e.g. delay and variable throughput. Compared to traditional and modern control methods where the dyn...
Article
Full-text available
In the last decade, Silicon carbide (SiC) has emerged as a potential material for high-frequency electronics and optoelectronics applications that may require elevated temperature processing. SiC exists in more than 200 different crystallographic forms, referred to as polytypes. Based on their remarkable physical and electrical characteristics, suc...
Conference Paper
Full-text available
Bio-analytical devices have gained importance over the past few years because of their application in rapid diagnostics and biochemical analysis. The integration of the Cyber-Physical System (CPS) concept with bio-analytical devices is essential to enable automation of the device. Modeling of CPS-based bio-analytical devices can provide a deeper un...
Preprint
Full-text available
DW is a high temperature direct solid-state bonding process that can be comprehensively used to bond various contact forming material with the high-performance semiconductor substrate. In this work, we deposited 60 µm thick-Al foil on n-type 4H-SiC; p-type 4H-SiC, and p-type 6H-SiC substrate with a novel technology; DW. The current-voltage (I-V) ch...
Article
Full-text available
High-throughput microflow cytometry has become a focal point of research in recent years. In particular, droplet microflow cytometry (DMFC) enables the analysis of cells reacting to different stimuli in chemical isolation due to each droplet acting as an isolated microreactor. Furthermore, at high flow rates, the droplets allow massive parallelizat...
Article
Full-text available
In recent years, additive manufacturing has steadily gained attention in both research and industry. Applications range from prototyping to small-scale production, with 3D printing offering reduced logistics overheads, better design flexibility and ease of use compared with traditional fabrication methods. In addition, printer and material costs ha...
Article
The diffusion welding (DW), known as the direct bonding technique could be more used as an alternative approach to developing silicon carbide (SiC) Schottky rectifiers to existing mainstream metallization contact technologies. Measured results for p-type 4H-SiC Schottky barrier diodes (SBD) are presented. And comprehensive numerical study to charac...
Article
Full-text available
The diffusion welding (DW) is a comprehensive mechanism that can be extensively used to develop silicon carbide (SiC) Schottky rectifiers as a cheaper alternative to existing mainstream contact forming technologies. In this work, the Schottky barrier diode (SBD) fabricated by depositing Al-Foil on the p-type 4H-SiC substrate with a novel technology...
Article
During the last decade, silicon carbide (SiC) and its heterostructures with other semiconductors have gained a significant importance for wide range of electronics applications. These structures are highly suitable for high frequency and high power applications in extremely high temperature environments. SiC exists in more than 200 different polycr...
Article
Full-text available
Carbon nanotubes (CNTs)-based sensors have gained significant importance due to their tremendous electrical and physical attributes. CNT-based gas sensors have high sensitivity, stability, and fast response time compared to that of solid-state sensors. On exposure to a large variety of organic and inorganic compounds, the conductivity of CNT change...
Article
Full-text available
During the last few years graphene has emerged as a potential candidate for electronics and optoelectronics applications due to its several salient features. Graphene is a smart material that responds to any physical change in its surrounding environment. Graphene has a very low intrinsic electronic noise and it can detect even a single gas molecul...
Article
Full-text available
The effect of low-temperature (up to 600°C) isothermal and isochronous annealing on the electrical characteristics of irradiated n-4H-SiC JBS Schottky diodes is studied. Irradiation is performed with 0.9-MeV electrons at a dose of 1 × 10¹⁶ cm–2. It is shown that the forward current–voltage (I–V) and capacitance–voltage (C–V) characteristics of the...
Article
Full-text available
In recent years, graphene has sparked the interest of researchers due to its promising electrical and physical attributes. These attributes make it highly suitable to develop electronic devices with ultra-high mobility of charge carriers. Meanwhile silicon carbide (SiC), a wide bandgap semiconductor material, is being used for high temperature opto...
Article
In the present work, the kinetics of low-temperature annealing (400 °C) of 4H-SiC JBS diodes irradiated by electrons with an energy of 0.9 MeV and with a dose of 1E16 cm ⁻² was studied. The dynamics of changes in I-V, C-V characteristics, as well as DLTS spectra are shown. In the course of the work, a thermal cycling effect was discovered, i.e., ef...
Article
Full-text available
In the last decades, silicon carbide (SiC) based heterostructures have gained a remarkable place in research field due to their exceptional properties. These properties make SiC highly suitable for high temperature, high frequency, and high power electronics applications. The most prominent polytypes (among 200 types) of SiC like 3C-SiC, 4H-SiC and...
Article
Full-text available
Nucleic acid amplification tests (NAAT) are widely used for the detection of living organisms, recently applied in Lab-on-a-Chip (LoC) devices to make portable DNA analysis platforms. While portable LoC-NAAT can provide definitive test results on the spot, it requires specialized temperature control equipment. This work focuses on delivering a gene...
Article
Full-text available
Over the last decade graphene based electronic devices have attracted the interest of researchers due to their exceptional chemical, electrical and optical properties. Graphene is very sensitive to any physical changes in its surrounding environment and, inherently, has very low electronic noise. This property of graphene makes it a suitable candid...
Article
Full-text available
Graphene has been employed as electrode materials in various electrochemical biosensors due to its excellent electrical, mechanical, thermal and optical properties. In the present study, Chemical Vapor Deposited (CVD) and epitaxial graphene on SiC were examined as material for electrochemical biosensing application. The surface of both types of gra...
Article
Full-text available
The effect of low-temperature (up to 600°C) isothermal and isochronous annealing on the electrical characteristics of irradiated n -4 H -SiC JBS Schottky diodes is studied. Irradiation is performed with 0.9-MeV electrons at a dose of 1 × 10^16 cm^–2. It is shown that the forward current–voltage ( I – V ) and capacitance–voltage ( C – V ) characteri...
Article
Full-text available
Rapidly increasing usage of telecommunication systems causes new transmission technologies and networks to emerge. Not only the efficiency, reliability and accessibility of the network are important, but also the economic issues. One cost-effective solution could be power line communication (PLC) technology, which transmits data using the existing...
Article
Full-text available
Novel second-generation rapid diagnostics based on nucleic acid amplification tests (NAAT) offer performance metrics on par with clinical laboratories in detecting infectious diseases at the point of care. The diagnostic assay is typically performed within a Lab-on-a-Chip (LoC) component with integrated temperature regulation. However, constraints...
Article
Full-text available
In the present work, the prototype of a voltage multiplier represented as the diffusion-welded stack is presented. Two options of multiplier prototypes are considered: the scheme with external capacitors and the multiplier of the vertical composition using the diode's own capacitance. Oscillograms of input and output signals for both multiplier com...
Article
Full-text available
In the last decade, silicon carbide (SiC) has gained a remarkable position among wide bandgap semiconductors due to its high temperature, high frequency, and high power electronics applications. SiC heterostructures, based on the most prominent polytypes like 3C-SiC, 4H-SiC and 6H-SiC, exhibit distinctive electrical and physical properties that mak...
Article
Full-text available
Over the last decade graphene and its derivatives have gained a remarkable place in research field. As silicon technology is approaching to its geometrical limits so there is a need of alternate that can replace it. Graphene has emerged as a potential candidate for future nano-electronics applications due to its exceptional and extraordinary chemic...
Data
Please ensure you have the latest version of COMSOL installed before you try to open this file! COMSOL 5.3 MPH file for article "Integrated self-regulating resistive heating for isothermal nucleic acid amplification tests (NAAT) in Lab-on-a-Chip (LoC) devices". Password "bela1234"
Article
Full-text available
Isothermal nucleic acid amplification tests (NAAT) in a Lab-on-a-Chip (LoC) format promise to bring high-accuracy, non-instrumented rapid tests to the point of care. Reliable rapid tests for infectious diseases allow for early diagnosis and treatment, which in turn enables better containment of potential outbreaks and fewer complications. A critica...
Data
Temperature data for BM117-83-A and -B lot PTCR polymer resin heater samples. (PDF)
Article
Purpose This paper aims to give a brief overview of dielectric properties, relative complex permittivity and its dependence on frequency. The significance of different approaches to complex permittivity is also discussed. Design/methodology/approach The different mechanisms of polarization are then presented. Dielectric measurements are given, a...
Poster
Full-text available
In the present work, the prototype of a voltage multiplier represented as the diffusion-welded stack is presented. Two options of multiplier prototypes are considered: the scheme with external capacitors and the multiplier of the vertical composition using the diode's own capacitance. Oscillograms of input and output signals for both multiplier com...
Article
Full-text available
Non-instrumented nucleic acid amplification tests (NINAAT) are a novel paradigm in portable molecular diagnostics. They offer the high detection accuracy characteristic of nucleic acid amplification tests (NAAT) in a self-contained device, without the need for any external instrumentation. These Point-of-Care tests typically employ a Lab-on-a-Chip fo...
Article
We considered the prototype of a SiC Schottky diode Rectifier Bridge made on the basis of commercial SiC Schottky diodes by diffusion welding (DW). Vertical integration for four diode chips in combination with molybdenum electrodes can improve the overall weight and dimensions of the module performance and increase device durability to radiation ex...
Article
Full-text available
Extracting useful information from cardiac signals for the diagnosis of diseases and judgement of heart functioning is of special interest to medical personnel. However, exploiting such signals is subject to the availability of the signals themselves and to possible measurement errors. We thus argue that modelling such signals offers several advant...
Conference Paper
Full-text available
Certain novel molecular diagnostics Point-of-Care applications require precise temperature control (±1–5 °C) over an extended time (15–60 minutes) for proper function. Microheating components in portable tests must meet strict criteria with respect to size and power consumption, both of which may be met with thermoelectric heating. Our proposed fin...
Conference Paper
Analog systems, where good and stable supply plays an important role in total system performance, need highly accurate, clean and reliable low dropout linear regulators (LDOs). High performance and low area are also important in voltage reference circuits for achieving smallest cost and best in the industry Analog-to-Digital (A/D) and Digital-to-An...
Conference Paper
In the work presented in this paper we have considered the prototype of a diffusion-welded (DW) high-voltage diode stack made on the basis of commercial SiC JBS diode chips. Implementation of vertical integration for four diode chips yielded a stack with a reverse current of 25 µA under a reverse voltage of 6 kV. The capacitance of the stack at zer...
Conference Paper
In this paper are proposed the technique of fragmentation of the p + -pin-n + structures and preparation of the samples for investigation of transient processes in the space charge region at the interfaces in pin structures. As an example, some results of capacitance-voltage (C-V) investigations and the results of capacity relaxation studies is pre...
Conference Paper
Full-text available
The number of disposable molecular diagnostics tests in the IVD market has been growing rapidly and is bound to continue to grow in the near future. The internal complexity of these rapid tests increases with the complexity of the diagnostic assay implemented by them. Some assays require precise temperature control (±1°C –5°C) for an extended time...
Article
Full-text available
In the present work we have considered the prototype of the high-voltage diode stack made on the basis of commercial SiC Schottky diodes. Implementation of vertical integration for four diode chips yielded stack with the reverse current of 25 μA under reverse voltage of 6 kV. The capacitance of the stack at zero bias is reduced more than three time...
Poster
Full-text available
Some of the assays actively developed in a Lab-on-a-Chip format require temperature control, mostly heating to a specified range for the duration of the assay. In a highly portable system with limited power supply, heating microliters of liquids poses technical challenges, which may be costly to overcome solely by experimental means. The way comput...
Conference Paper
Full-text available
Resistive heating elements based on positive temperature coefficient (PTC) ceramics have the inherent advantage of self-regulating their temperature output via a rapid increase in resistance with increasing temperatures, and therefore require no additional control circuitry. This is particularly advantageous for medical devices, especially disposab...
Conference Paper
Full-text available
The bonding of crystallic semiconductor structures for getting polytypic heterojunctions on the basis of wide band gap semiconductor materials has considerably increased. The direct wafer bonding technology for the creation of polytypic heterojunctions (e.g. silicon carbide polytypes like 4H-SiC, 6H-SiC, 3C-SiC) gives an advantage in obtaining hete...
Conference Paper
Full-text available
This paper is devoted to the analysis of Deep Level Transient Spectroscopy (DLTS) of the background deep levels in GaAs p +-p-in -n + structures. It is known that A and B centers are observed in epitaxial layers of GaAs, grown by LPE in a hydrogen atmosphere. These two deep acceptor levels determine the minority carrier lifetime and the reverse rec...
Conference Paper
Full-text available
We present a finite element model for the simulation of the resistive heating of microchannels in disposable molecular diagnostics devices by means of various resistive heating elements, and demonstrate the validity of this model through experiments. Polyimide etched foil heaters and heaters based on positive temperature coefficient (PTC) ceramics...
Conference Paper
Full-text available
Deep level traps in the forbidden bandgap of semiconductor can be either a desired effect or technological harm that should be avoided. Understanding the essence of specific deep traps, their influence on electrical optical and mechanical characteristics of devices and circuits makes it possible to drive the manufacturing processes to maximize the...
Conference Paper
Full-text available
This work presents the results of capacitance-voltage (C-V), current-voltage (I-V) and deep level transient spectroscopy (DLTS) on special Schottky diode samples fabricated on the basis of GaAs p+-pin-n+ structure. It is shown that in the i-layer and n-region bordering the i-layer is observed "anomalous" stationary capacitance temperature change. D...
Conference Paper
High performance low dropout regulator (LDO) is presented in this paper. An analysis of low noise architecture incorporating reference amplifier followed by a low-pass filter (LPF) and an error amplifier (EA) connected as a voltage follower is done, with a special focus on the low voltage operation implementation. By introduction of special design...
Conference Paper
Full-text available
The field of micro-electro-mechanical-systems (MEMS) grew out from the integrated circuit (IC) industry. So far the main fabrication techniques used in MEMS are planar technologies, which set limitations to the sensor/actuator design. Therefore greyscale (3D) technology seems to be the method for fabrication of three-dimensional structures in a sin...
Article
This paper presents an analysis of the DLTS (Deep Level Transient Spectroscopy) spectra of GaAs p+-pin-n+diodes. It is shown that the background spectrum of the deep levels is reproducible and depends on the liquid-phase epitaxy mode (LPE). The temperature dependence of the capacitancevoltage characteristics showed that the i layer is formed by com...