Special Issue "Applications of Thin Films in Microelectronics"

A special issue of Electronics (ISSN 2079-9292). This special issue belongs to the section "Microelectronics".

Deadline for manuscript submissions: 31 January 2022.

Special Issue Editor

Dr. Hyuk-Jun (Jaden) Kwon
E-Mail Website
Guest Editor
Department of Information & Communication Engineering (ICE), DGIST, Daegu 42988, Korea
Interests: flexible and wearable electronics and applications; Site-selective laser processing (annealing, sintering, direct laser writing, plasmonic welding, interference, etc.); micro/nanoscale thermal/heat transfer analysis; polymer like hyperelastic non-linear behavior analysis (e.g. stress, strain) for stretchable and flexible structure; electronic and optoelectronic device applications of 2D materials; device physics for semiconductor devices based on thin-film transistors platform; solution processed low-cost printing technologies and development (e.g. screen, inkjet, roll-to-roll, gravure, etc.); 3D hierarchical mechanical metamaterial structure and system

Special Issue Information

Dear Colleagues,

Thin films formed by lots of different approaches are being used in various applications for microelectronics (e.g., transistors, sensors, batteries, energy devices, actuators, coatings) due to their versatility. Furthermore, the electronics industry has become the greatest beneficiary of thin film technology, which contributes to the development of microelectronics by reducing the sizes of semiconductor devices. These thin film devices are more essentially designed, with outstanding mechanical deformability, sensitive-to-multifunctional responses, and intelligent control capabilities. As thin films technology is a multidisciplinary field, thin films studies have directly or indirectly caused the advancement of many new areas of research and will continue to play increasingly important roles in the study of a variety of problems of basic and technological importance. Therefore, by interacting with diverse perspectives, knowledge of the nature, functions, and new properties of thin films can be used for the development of new technologies for future applications in microelectronics.

The main aim of this Special Issue is to seek high-quality submissions that highlight emerging applications, materials synthesis, and the fabrication process, which address recent breakthroughs in the microelectronic system. The topics of interest include but are not limited to:

  • Searching and investigating various types of applications of thin films in electronics;
  • Advanced fabrication processes and characterizations;
  • Research into new synthesis methods;
  • Analysis of film behaviors;
  • Robust and reliable novel geometrical designs in microelectronics.

Dr. Hyuk-Jun (Jaden) Kwon
Guest Editor

Manuscript Submission Information

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Keywords

  • Applications of thin films in electronics
  • Low dimension materials
  • Advanced fabrication processes
  • Analysis of film behaviors (Physical and chemical)
  • Robust and reliable structural design
  • Characterizations of thin films
  • New synthesis approach

Published Papers (12 papers)

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Research

Article
Ferroelectric Induced UV Light-Responsive Memory Devices with Low Dark Current
Electronics 2021, 10(16), 1897; https://doi.org/10.3390/electronics10161897 - 07 Aug 2021
Viewed by 692
Abstract
We developed solution-processed hybrid photodetectors with a poly (9-vinylcarbazole)/zinc oxide nanoparticle photoactive layer and a poly (vinylidene fluoride-co-trifluoroethylene) ferroelectric copolymer buffer layer on flexible plastic substrates. The presence of a ferroelectric-poling interface layer significantly enhanced the charge transfer and responsivity of the photodetectors [...] Read more.
We developed solution-processed hybrid photodetectors with a poly (9-vinylcarbazole)/zinc oxide nanoparticle photoactive layer and a poly (vinylidene fluoride-co-trifluoroethylene) ferroelectric copolymer buffer layer on flexible plastic substrates. The presence of a ferroelectric-poling interface layer significantly enhanced the charge transfer and responsivity of the photodetectors under ultraviolet (UV, 365 nm) light exposure. The responsivity of the device reached 250 mA/W at a reverse bias of 5 V and incident light intensity of 27.5 μW/cm2. This responsivity was four times higher than that of a device without the ferroelectric copolymer layer (64 mA/W) under the same conditions. The response time of the device to incident UV light also improved from 322 to 34 ms with the addition of the ferroelectric copolymer layer. In addition, the flexible device exhibited a stable performance in an air environment up to a maximum strain of 0.3 under bending stress. Finally, a UV-light-responsive memory device was successfully fabricated by using the developed hybrid photodetector and liquid crystals. This device showed a colour change from white to black upon UV illumination, and the on-state of the device was maintained for 30 s without light exposure owing to the polarization of poly (vinylidene fluoride-co-trifluoroethylene). Full article
(This article belongs to the Special Issue Applications of Thin Films in Microelectronics)
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Article
Improved Negative Bias Stress Stability of Sol–Gel-Processed Li-Doped SnO2 Thin-Film Transistors
Electronics 2021, 10(14), 1629; https://doi.org/10.3390/electronics10141629 - 08 Jul 2021
Viewed by 582
Abstract
In this study, sol–gel-processed Li-doped SnO2-based thin-film transistors (TFTs) were fabricated on SiO2/p+ Si substrates. The influence of Li dopant (wt%) on the structural, chemical, optical, and electrical characteristics was investigated. By adding 0.5 wt% Li dopant, the oxygen [...] Read more.
In this study, sol–gel-processed Li-doped SnO2-based thin-film transistors (TFTs) were fabricated on SiO2/p+ Si substrates. The influence of Li dopant (wt%) on the structural, chemical, optical, and electrical characteristics was investigated. By adding 0.5 wt% Li dopant, the oxygen vacancy formation process was successfully suppressed. Its smaller ionic size and strong bonding strength made it possible for Li to work as an oxygen vacancy suppressor. The fabricated TFTs consisting of 0.5 wt% Li-doped SnO2 semiconductor films delivered the field-effect mobility in a 2.0 cm2/Vs saturation regime and Ion/Ioff value of 1 × 108 and showed enhancement mode operation. The decreased oxygen vacancy inside SnO2 TFTs with 0.5 wt% Li dopant improved the negative bias stability of TFTs. Full article
(This article belongs to the Special Issue Applications of Thin Films in Microelectronics)
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Article
Effects of Active Layer Thickness on the Electrical Characteristics and Stability of High-Mobility Amorphous Indium–Gallium–Tin Oxide Thin-Film Transistors
Electronics 2021, 10(11), 1295; https://doi.org/10.3390/electronics10111295 - 28 May 2021
Viewed by 725
Abstract
Herein, we investigated the effects of active layer thickness (tS) on the electrical characteristics and stability of high-mobility indium–gallium–tin oxide (IGTO) thin-film transistors (TFTs). IGTO TFTs, with tS values of 7 nm, 15 nm, 25 nm, 35 nm, and [...] Read more.
Herein, we investigated the effects of active layer thickness (tS) on the electrical characteristics and stability of high-mobility indium–gallium–tin oxide (IGTO) thin-film transistors (TFTs). IGTO TFTs, with tS values of 7 nm, 15 nm, 25 nm, 35 nm, and 50 nm, were prepared for this analysis. The drain current was only slightly modulated by the gate-to-source voltage, in the case of the IGTO TFT with tS = 50 nm. Under positive bias stress (PBS), the electrical stability of the IGTO TFTs with a tS less than 35 nm improved as the tS increased. However, the negative bias illumination stress (NBIS) stability of these IGTO TFTs deteriorated as the tS increased. To explain these phenomena, we compared the O1s spectra of IGTO thin films with different tS values, acquired using X-ray photoelectron spectroscopy. The characterization results revealed that the better PBS stability, and the low NBIS stability, of the IGTO TFTs with thicker active layers were mainly due to a decrease in the number of hydroxyl groups and an increase in the number of oxygen vacancies in the IGTO thin films with an increase in tS, respectively. Among the IGTO TFTs with different tS, the IGTO TFT with a 15-nm thick active layer exhibited the best electrical characteristics with a field-effect mobility (µFE) of 26.5 cm2/V·s, a subthreshold swing (SS) of 0.16 V/dec, and a threshold voltage (VTH) of 0.3 V. Moreover, the device exhibited robust stability under PBS (ΔVTH = 0.9 V) and NBIS (ΔVTH = −1.87 V). Full article
(This article belongs to the Special Issue Applications of Thin Films in Microelectronics)
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Article
Influence of Active Channel Layer Thickness on SnO2 Thin-Film Transistor Performance
Electronics 2021, 10(2), 200; https://doi.org/10.3390/electronics10020200 - 17 Jan 2021
Cited by 1 | Viewed by 932
Abstract
Sol-gel processed SnO2 thin-film transistors (TFTs) were fabricated on SiO2/p+ Si substrates. The SnO2 active channel layer was deposited by the sol-gel spin coating method. Precursor concentration influenced the film thickness and surface roughness. As the concentration of [...] Read more.
Sol-gel processed SnO2 thin-film transistors (TFTs) were fabricated on SiO2/p+ Si substrates. The SnO2 active channel layer was deposited by the sol-gel spin coating method. Precursor concentration influenced the film thickness and surface roughness. As the concentration of the precursor was increased, the deposited films were thicker and smoother. The device performance was influenced by the thickness and roughness of the SnO2 active channel layer. Decreased precursor concentration resulted in a fabricated device with lower field-effect mobility, larger subthreshold swing (SS), and increased threshold voltage (Vth), originating from the lower free carrier concentration and increase in trap sites. The fabricated SnO2 TFTs, with an optimized 0.030 M precursor, had a field-effect mobility of 9.38 cm2/Vs, an SS of 1.99, an Ion/Ioff value of ~4.0 × 107, and showed enhancement mode operation and positive Vth, equal to 9.83 V. Full article
(This article belongs to the Special Issue Applications of Thin Films in Microelectronics)
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Article
Investigation of Structural and Optoelectronic Properties of Organic Semiconductor Film Based on 8-Hydroxyquinoline Zinc
Electronics 2021, 10(2), 117; https://doi.org/10.3390/electronics10020117 - 08 Jan 2021
Viewed by 691
Abstract
In this work, we investigated an organic semiconductor based on zinc 8-hydroxyquinoline (ZnQ2) and tetracyanoquinodimethane (TCNQ), which can be used as a photoactive layer in organic devices. The semiconductor was optimized by applying density-functional theory (DFT) methods, and four hydrogen bridges [...] Read more.
In this work, we investigated an organic semiconductor based on zinc 8-hydroxyquinoline (ZnQ2) and tetracyanoquinodimethane (TCNQ), which can be used as a photoactive layer in organic devices. The semiconductor was optimized by applying density-functional theory (DFT) methods, and four hydrogen bridges were formed between ZnQ2 and TCNQ. Later, thin films of ZnQ2-TCNQ were successfully deposited. The films were structurally and morphologically characterized, and the optical characteristics of the photoactive layer were investigated using ultraviolet–visible spectroscopy and time-dependent density-functional theory (TDDFT) calculations. The comparison and analysis of the experimental and theoretical absorption spectra indicate that the optical bandgap of the photoactive layer is 2.4 eV. Additionally, a flexible photo device was manufactured with the active layer ZnQ2-TCNQ, and its electrical behavior was evaluated under dark and light conditions. The results show a significant change in the behavior of the device when radiation is eliminated; the layer is light sensitive. The electrical resistance in the flexible photo device is associated with the optical behavior of the materials that constitute the active layer. Full article
(This article belongs to the Special Issue Applications of Thin Films in Microelectronics)
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Article
Electrical Performance and Stability Improvements of High-Mobility Indium–Gallium–Tin Oxide Thin-Film Transistors Using an Oxidized Aluminum Capping Layer of Optimal Thickness
Electronics 2020, 9(12), 2196; https://doi.org/10.3390/electronics9122196 - 20 Dec 2020
Cited by 1 | Viewed by 845
Abstract
We examined the effects of aluminum (Al) capping layer thickness on the electrical performance and stability of high-mobility indium–gallium–tin oxide (IGTO) thin-film transistors (TFTs). The Al capping layers with thicknesses (tAls) of 3, 5, and 8 nm were deposited, respectively, [...] Read more.
We examined the effects of aluminum (Al) capping layer thickness on the electrical performance and stability of high-mobility indium–gallium–tin oxide (IGTO) thin-film transistors (TFTs). The Al capping layers with thicknesses (tAls) of 3, 5, and 8 nm were deposited, respectively, on top of the IGTO thin film by electron beam evaporation, and the IGTO TFTs without and with Al capping layers were subjected to thermal annealing at 200 °C for 1 h in ambient air. Among the IGTO TFTs without and with Al capping layers, the TFT with a 3 nm thick Al capping layer exhibited excellent electrical performance (field-effect mobility: 26.4 cm2/V s, subthreshold swing: 0.20 V/dec, and threshold voltage: −1.7 V) and higher electrical stability under positive and negative bias illumination stresses than other TFTs. To elucidate the physical mechanism responsible for the observed phenomenon, we compared the O1s spectra of the IGTO thin films without and with Al capping layers using X-ray photoelectron spectroscopy analyses. From the characterization results, it was observed that the weakly bonded oxygen-related components decreased from 25.0 to 10.0%, whereas the oxygen-deficient portion was maintained at 24.4% after the formation of the 3 nm thick Al capping layer. In contrast, a significant increase in the oxygen-deficient portion was observed after the formation of the Al capping layers having tAl values greater than 3 nm. These results imply that the thicker Al capping layer has a stronger gathering power for the oxygen species, and that 3 nm is the optimum thickness of the Al capping layer, which can selectively remove the weakly bonded oxygen species acting as subgap tail states within the IGTO. The results of this study thus demonstrate that the formation of an Al capping layer with the optimal thickness is a practical and useful method to enhance the electrical performance and stability of high-mobility IGTO TFTs. Full article
(This article belongs to the Special Issue Applications of Thin Films in Microelectronics)
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Communication
Effects of Annealing Atmosphere on Electrical Performance and Stability of High-Mobility Indium-Gallium-Tin Oxide Thin-Film Transistors
Electronics 2020, 9(11), 1875; https://doi.org/10.3390/electronics9111875 - 07 Nov 2020
Cited by 3 | Viewed by 1122
Abstract
In this study, we examined the effects of the annealing atmosphere on the electrical performance and stability of high-mobility indium-gallium-tin oxide (IGTO) thin-film transistors (TFTs). The annealing process was performed at a temperature of 180 °C under N2, O2, [...] Read more.
In this study, we examined the effects of the annealing atmosphere on the electrical performance and stability of high-mobility indium-gallium-tin oxide (IGTO) thin-film transistors (TFTs). The annealing process was performed at a temperature of 180 °C under N2, O2, or air atmosphere after the deposition of IGTO thin films by direct current magnetron sputtering. The field-effect mobility (μFE) of the N2- and O2-annealed IGTO TFTs was 26.6 cm2/V·s and 25.0 cm2/V·s, respectively; these values were higher than that of the air-annealed IGTO TFT (μFE = 23.5 cm2/V·s). Furthermore, the stability of the N2- and O2-annealed IGTO TFTs under the application of a positive bias stress (PBS) was greater than that of the air-annealed device. However, the N2-annealed IGTO TFT exhibited a larger threshold voltage shift under negative bias illumination stress (NBIS) compared with the O2- and air-annealed IGTO TFTs. The obtained results indicate that O2 gas is the most suitable environment for the heat treatment of IGTO TFTs to maximize their electrical properties and stability. The low electrical stability of the air-annealed IGTO TFT under PBS and the N2-annealed IGTO TFT under NBIS are primarily attributed to the high density of hydroxyl groups and oxygen vacancies in the channel layers, respectively. Full article
(This article belongs to the Special Issue Applications of Thin Films in Microelectronics)
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Article
Polarization-Charge Inversion at Al2O3/GaN Interfaces through Post-Deposition Annealing
Electronics 2020, 9(7), 1068; https://doi.org/10.3390/electronics9071068 - 30 Jun 2020
Viewed by 1128
Abstract
The effects of post-deposition annealing (PDA) on the formation of polarization-charge inversion at ultrathin Al2O3/Ga-polar GaN interfaces are assessed by the analysis of energy band bending and measurement of electrical conduction. The PDA-induced positive interface charges form downward energy [...] Read more.
The effects of post-deposition annealing (PDA) on the formation of polarization-charge inversion at ultrathin Al2O3/Ga-polar GaN interfaces are assessed by the analysis of energy band bending and measurement of electrical conduction. The PDA-induced positive interface charges form downward energy band bending at the Al2O3/GaN interfaces with polarization-charge inversion, which is analyzed using X-ray photoelectron spectroscopy. Net charge and interface charge densities at the Al2O3/GaN interfaces are estimated after PDA at 500 °C, 700 °C, and 900 °C. The PDA temperatures affect the formation of charge densities. That is, the charge density increases up to 700 °C and then decreases at 900 °C. Electrical characteristics of GaN Schottky diodes with ultrathin Al2O3 layers exhibit the passivation ability of the Al2O3 surface layer and the effects of polarization-charge inversion through PDA. This result can be applied to improvement in GaN-based electronic devices where surface states and process temperature work important role in device performance. Full article
(This article belongs to the Special Issue Applications of Thin Films in Microelectronics)
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Article
Effect of Mg Doping on the Electrical Performance of a Sol-Gel-Processed SnO2 Thin-Film Transistor
Electronics 2020, 9(3), 523; https://doi.org/10.3390/electronics9030523 - 22 Mar 2020
Cited by 6 | Viewed by 1444
Abstract
Sol-gel-processed Mg-doped SnO2 thin-film transistors (TFTs) were successfully fabricated. The effect of Mg concentration on the structural, chemical, and optical properties of thin films and the corresponding TFT devices was investigated. The results indicated that an optimal Mg concentration yielded an improved [...] Read more.
Sol-gel-processed Mg-doped SnO2 thin-film transistors (TFTs) were successfully fabricated. The effect of Mg concentration on the structural, chemical, and optical properties of thin films and the corresponding TFT devices was investigated. The results indicated that an optimal Mg concentration yielded an improved negative bias stability and increased optical band gap, resulting in transparent devices. Furthermore, the optimal device performance was obtained with 0.5 wt% Mg. The fabricated 0.5 wt% Mg-doped SnO2 TFT was characterized by a field effect mobility, a subthreshold swing, and Ion/Ioff ratio of 4.23 cm2/Vs, 1.37 V/decade, and ~1 × 107, respectively. The added Mg suppressed oxygen-vacancy formation, thereby improving the bias stability. This work may pave the way for the development of alkaline-earth-metal-doped SnO2-based thin-film devices. Full article
(This article belongs to the Special Issue Applications of Thin Films in Microelectronics)
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Article
Sol-Gel Processed Yttrium-Doped SnO2 Thin Film Transistors
Electronics 2020, 9(2), 254; https://doi.org/10.3390/electronics9020254 - 03 Feb 2020
Cited by 5 | Viewed by 1545
Abstract
Y-doped SnO2 thin film transistors were successfully fabricated by means of sol-gel process. The effect of Y concentration on the structural, chemical, and electrical properties of sol-gel-processed SnO2 films was investigated via GIXRD, SPM, and XPS; the corresponding electrical transport properties [...] Read more.
Y-doped SnO2 thin film transistors were successfully fabricated by means of sol-gel process. The effect of Y concentration on the structural, chemical, and electrical properties of sol-gel-processed SnO2 films was investigated via GIXRD, SPM, and XPS; the corresponding electrical transport properties of the film were also evaluated. The dopant, Y, can successfully control the free carrier concentration by suppressing the formation of oxygen vacancy inside SnO2 semiconductors due to its lower electronegativity and SEP. With an increase of Ywt%, it was observed that the crystallinity and oxygen vacancy concentration decreased, and the operation mode of SnO2 thin film transistor changed from accumulation (normally on) to enhancement mode (normally off) with a positive Vth shift. Full article
(This article belongs to the Special Issue Applications of Thin Films in Microelectronics)
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Article
Effect of Annealing Ambient on SnO2 Thin Film Transistors Fabricated via An Ethanol-based Sol-gel Route
Electronics 2019, 8(9), 955; https://doi.org/10.3390/electronics8090955 - 29 Aug 2019
Cited by 7 | Viewed by 1262
Abstract
The effect of annealing ambient on SnO2 thin-film transistors (TFTs) fabricated via an ethanol-based sol-gel route was investigated. The annealing ambient has a significant effect on the structural characteristics and chemical composition and, in turn, the device performance. Although the crystalline-grain size [...] Read more.
The effect of annealing ambient on SnO2 thin-film transistors (TFTs) fabricated via an ethanol-based sol-gel route was investigated. The annealing ambient has a significant effect on the structural characteristics and chemical composition and, in turn, the device performance. Although the crystalline-grain size of the SnO2 films annealed in air was the smallest, this size yielded the highest field-effect mobility. Compared with the minimization of boundary scattering via crystalline-size increase, augmentation of the free carrier concentration played a more critical role in the realization of high-performance devices. The fabricated SnO2 TFTs delivered a field-effect mobility, subthreshold swing, and on/off current ratio of 10.87 cm2/Vs, 0.87 V/decade, and 107, respectively. Full article
(This article belongs to the Special Issue Applications of Thin Films in Microelectronics)
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Article
Effect of Annealing Environment on the Performance of Sol–Gel-Processed ZrO2 RRAM
Electronics 2019, 8(9), 947; https://doi.org/10.3390/electronics8090947 - 28 Aug 2019
Cited by 5 | Viewed by 1594
Abstract
We investigate the annealing environment effect on ZrO2-based resistive random-access memory (RRAM) devices. Fabricated devices exhibited conventional bipolar-switching memory properties. In particular, the vacuum-annealed ZrO2 films exhibited larger crystallinity and grain size, denser film, and a relatively small quantity of [...] Read more.
We investigate the annealing environment effect on ZrO2-based resistive random-access memory (RRAM) devices. Fabricated devices exhibited conventional bipolar-switching memory properties. In particular, the vacuum-annealed ZrO2 films exhibited larger crystallinity and grain size, denser film, and a relatively small quantity of oxygen vacancies compared with the films annealed in air and N2. These led to a decrease in the leakage current and an increase in the resistance ratio of the high-resistance state (HRS)/low-resistance state (LRS) and successfully improved non-volatile memory properties, such as endurance and retention characteristics. The HRS and LRS values were found to last for 104 s without any significant degradation. Full article
(This article belongs to the Special Issue Applications of Thin Films in Microelectronics)
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