bluuebunny/crossref_metadata_2025_split huggingface dataset:
Device-Level Impact of Highly Anisotropic Thermal Conductivity of AlN/GaN Digital Alloys
Authors: Aller Henry Tyler , Chaney Alexander , Pfeifer Thomas , Averett Kent , Asel Thaddeus , Hopkins Patrick E , Mou Shin , Graham Samuel 
Published: November 2022

AlN/GaN digital alloys (i.e., short period superlattices) have the advantage of being an ultra-wide bandgap due to the quantum confinement effect, preservation of high mobility (no strong alloy scattering), and higher thermal conductivity than AlGaN random alloys.
Herein, we investigate the influence of AlN/GaN thickness combinations on digital alloy (DA) thermal conductivity. Using time-domain thermoreflectance and steady-state thermoreflectance, we measure the anisotropic thermal conductivity of AlN/GaN DA’s, with thickness combinations: (2 nm/1 nm), (4 nm/1 nm), (6 nm/1 nm), (11 nm/1 nm). DA's with thick AlN layers exhibit highly anisotropic thermal conductivity (i.e., 4x difference between cross-plane and in-plane).
Using finite-element modeling, we thermally simulate AlGaN and AlN/GaN DA devices. Improved lateral heat spreading in DA devices results in lower hot-spot temperatures compared to AlGaN devices. As the first thermal measurements of AlN/GaN DA’s, this study provides guidance for future device design.
(Invited) Spin and Optical Properties of the Silicon Vacancy in 4H-SiC for Quantum Science and Technology
Authors: Carter Samuel G , Lekavicius Ignas , Banks Hunter B , Soykal Oney O , Pavunny Shojan P , Pennachio Dan , Hajzus Jenifer R , DeJarld Matt T , Yeats Andrew L , Brereton Peter G , Glaser Evan R , Purdy Andrew P , Bielejec Ed , Myers-Ward Rachael L , Gaskill David Kurt , Reinecke Thomas L 
Published: November 2022

Silicon vacancies in SiC are of significant interest for quantum information and sensing due to their unusual combination of long spin coherence time, optical addressability, and room-temperature operation in an industrially-relevant semiconductor. We characterize the spin and optical properties of the V2 silicon vacancy in 4H-SiC for both single defects and ensembles. We also show that they can be deterministically placed with sub-micron precision using focused Li ion implantation. Low-temperature photoluminescence excitation spectroscopy of the spin-dependent optical transitions of single silicon vacancies reveals two sharp lines with linewidths near the radiative lifetime limit. These lines correspond to the ms=±1/2 and ms=±3/2 states of an S=3/2 spin system that can be optically initialized, coherently manipulated with RF pulses, and read out via spin-dependent photoluminescence. We measure the different properties of spins in the two bases, and compare them to theoretical models. To suppress the limiting effects of the nuclear spin bath, we grow isotopically purified SiC with a very low abundance of 29Si and 13C. Our room temperature spin coherence measurements show orders-of-magnitude improvement of the coherence times in these materials. In particular, the inhomogeneous dephasing time T2
* in the ms=±1/2 basis shows a ~100x improvement, reaching 20 μs. We consider the prospects of this system for quantum sensing and as an efficient spin-photon interface for use in quantum networks.
This work was supported by the U.S. Office of Naval Research, the OSD Quantum Sciences and Engineering Program, the Defense Threat Reduction Agency, and the Center for Integrated Nanotechnologies, an Office of Science User Facility operated for the U.S. Department of Energy (DOE) Office of Science. Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA-0003525.
(Invited, Digital Presentation) Nondegenerate Hydrogen-Doped Polycrystalline Indium Oxide (InOx:H) Thin Films for High-Mobility Thin Film Transistors
Authors: Furuta Mamoru , Magari Yusaku 
Published: November 2022

Transparent metal oxide semiconductors (OSs) have been extensively investigated for use as the active channel layer of thin film transistors (TFTs) for next-generation flat-panel displays, nonvolatile memories, image sensors, and pH sensors, to name a few. Among OSs, the amorphous In–Ga–Zn–O (IGZO) has attracted particular attention for TFT applications owing to its high field effect mobility (μFE) of more than 10 cm2V−1s−1, steep subthreshold swing (S.S.), extremely low off-state current, large-area uniformity, and good bias stress stability. Although the μFE of an IGZO TFT is approximately one order of magnitude higher than that of an amorphous Si TFT, further improvement of the μFE of OS TFTs is required to expand their range of applications as an alternative to polycrystalline Si TFT.
Single-crystalline In2O3 has a Hall mobility as high as 160 cm2V−1s−1, which makes amorphous (a-) or polycrystalline (poly-) InOx a potential material for enhancing the μFE of OS TFTs. However, undoped InOx thin films is known as a degenerate semiconductor with high background electron density of over 1020 cm-3, which is attributed to the presence of native defects, such as oxygen vacancies, making them unsuitable for a channel material of OS TFTs.
In this presentation, nondegenerate hydrogen-doped polycrystalline InOx (poly-InOx:H) thin films were successfully prepared by low-temperature solid phase crystallization (SPC). A degenerate amorphous InOx:H thin film was deposited by sputtering in Ar, O2, and H2 gases, and an amorphous to polycrystalline phase transition (SPC) of the film was achieved after PDA at more than 175 °C. By PDA at 250 °C in air, a nondegenerate poly-InOx:H film could be obtained with a carrier density as low as 2.4 × 1017 cm−3, which is approximately three orders of magnitude lower than that of the initial a-InOx:H film. The TFTs with a 50 nm thick nondegenerate poly-InOx:H channel could be fully depleted by a gate electric field. A maximum μFE of 125.7 cm2V−1s−1 was exhibited by the TFT with the poly-InOx:H channel. The use of a nondegenerate poly-InOx:H film is a promising approach to boost the μFE of OS TFTs.
UV/Ozone Based Facile Surface Modulation Technique for Efficient Organic Thin Film Transistor
Authors: Shaharukh Sk , Dhar Achintya 
Published: November 2022

The capacity to actualize a comprehensive range of electronic functions based on organic devices is important to the development of fully functional organic electronic circuits. Specifically low voltage, quick switching transistors, in particular, have previously been demonstrated but a critical function, i.e. dependable data storage, is currently lacking. Organic thin-film transistors (OTFTs) have received a lot of interest for possible use in memory, flexible electronics such as sensors, and light-emitting diodes because of their inexpensive production costs, lightweight, mechanical flexibility, and other advantages.
The most often utilised active ingredient in organic TFTs is pentacene (C22H14). The electrical properties of organic TFTs based upon pentacene, such as field-effect mobility, are equivalent to those of amorphous silicon thin film transistors (a-Si TFTs), which are typically employed for the backplane of liquid crystal displays (LCDs), but far inferior to those of generic inorganic TFTs. As a result, electrical properties for high-performance flexible electronics must be improved. The interfacial properties of active layer and gate insulator layer plays a very crucial role in determining the electrical properties of organic TFTs. Therefore in this work we report an UV/ozone treatment on the surface of gate dielectric layer so as to improve the interfacial properties.
At first the glass substrate was cleaned in an ultrasonic cleaner with acetone, ethanol, isopropyl alcohol and DI water. Then by using thermal evaporation technique a gate electrode with thickness of approximately 80 nm was deposited on the substrate. Later a solution of Poly 4-vinylphenol (PVP) was spin coated with a thickness of 140 nm, this organic layer was deposited as the bottom insulator layer. Now an ozone treatment (wavelength = 253nm) for 5,10 and 20 min was done over the PVP layer. Subsequently a layer of PMMA was coated over the UV treated layer. Finally with a coating of 70nm thick pentacene active layer 100 nm thick silver drain/source electrodes with channel length of 50µm were also deposited using thermal deposition.
Further the morphology and topography was studied using AFM images and element analysis was done from XPS spectra. The device performance (output and transfer characteristics) was characterized using Kiethley 4200 SCS semiconductor parameter analyser. The changes in performance of transistor devices before and after UV/ozone treatment could be explained using XPS spectra, AFM images and water contact angle measurement. It is evident from the AFM images that the grain size of pentacene on UV/Ozone treated dielectric surface are larger than the untreated surface, thus reducing the boundary scattering and enhancing the field effect mobility. Thus surface treatment with UV/Ozone could acts as simple, low cost method to enhance the performance of a organic thin film transistors.
(Invited) Vertical Transparent ZnO TFT Based on a Stack of Thin-Films Deposited in Solution
Authors: Mohammed-Brahim Tayeb , Hussain Sajid , Wei Lei 
Published: November 2022

A lot of works are devoted now to integrate driving TFT with OLED, minimizing the area of the pixel. In other part, people try to fabricate devices using low cost technologies as deposition in solution avoiding any photolithography step in the process. Finally, it can be better if the full driving TFT-OLED device is transparent.
The present work try to answer simultaneously to these 3 desires. Particularly, the present paper focus on the TFT.
Vertical TFT will answer to the first desire to minimize the area of the device. It is based here on a stack of the gate, the insulator, the source, the semiconducting active layer and the drain; meaning 5 films all solution deposited.
Thanks to the present available insulator solutions for the deposition, different insulators can be chosen. High k HFO2 insulator is chosen in this work. It is is spincoated and then annealed at 300C during 1 hour. Figure 1 shows the current-voltage curves of ITO/HFO2/AgNWs stack. After rapid increase, the current stabilizes at 10 pAmp at least still a voltage of 10V, meaning a field of 7.7x105 V/cm2 with a thickness of 130 nm. Present HFO2 film is then a good insulator.
ZnO is chosen as active layer. It is spin-coated and then annealed at 180C. This temperature was found enough high to lower the conductivity (Figure 2)
The source and drain layers are spin-coated using Ag nanowires (AgNWs) solution. As source AgNWs layer is deposited before ZnO layer, it will be annealed at the same temperature 180C. Figure 3 shows that AgNWs film stays enough conducting after such annealing temperature. It can be used as conducting source and drain.
Finally, the full stack of 5 films is characterized as a TFT.
Figure 4 shows the transfer characteristic of this TFT plotted at a drain voltage of 2.6V. The drain current is modulated by 4 orders from off to on regime.
Very simple and low cost fully in solution process is presented in this work. Working transparent TFT is demonstrated. The process shows its high potential in the development of integrated TFT-OLED in small area. It is very promising.
Its shows also the need of future hard work in this way to demonstrate fully integrated driving TFT-OLED

Figure 1
(Invited) Metallic Transport Behaviors in Monolayer and Multi-Layer MoS2 By Surface-Charge Transfer Interaction with Redox-Active Molecules
Authors: Kiriya Daisuke 
Published: November 2022

In the last decade, transition metal chalcogenides (TMDCs), e.g., MoS2 and WSe2, have gathered attention as semiconducting 2D materials. Modulation of carrier concentrations in TMDCs is a crucial matter for applying to semiconductor devices. So far, we have developed a method to gain the carrier concentrations of MoS2 by a junction with organic molecules and achieved obtaining a degenerately doped state in the MoS2. The mechanism of the doping is a surface-charge transfer interaction at the interface. Although the transfer characteristic behaviors show the degenerately doped state (small ON/OFF ratio), the details of the transport behavior have not been well understood. In this presentation, I will discuss the details of the device characteristics of the monolayer and multilayer MoS2 metal-oxide-semiconductor field-effect-transistors (MOSFETs) with a junction of redox-active molecules in a manner of the surface-charge transfer interaction. The devices were fabricated via standard lithography (e-beam and photolithography) techniques to prepare each monolayer and multilayer MoS2 MOSFETs. Transport properties in the MoS2 MOSFETs were measured in the as-prepared device and the device after the molecular doping. The dopant molecule is benzyl viologen (BV) molecule which is known as a redox-active molecule with high-reduction potential. After the doping with BV molecules, the MoS2 MOSFET showed a small ON/OFF ratio in the transfer characteristic curves, indicating a degenerately doped state. The identical device further showed the metallic behavior in the temperature dependence (the conductivity increases with decreasing the temperature). Both monolayer and multilayer MoS2 MOSFETs showed similar metallic behavior. This metallic transport behavior changes to an insulative regime when applying gate-voltage to reduce the carrier concentrations in the channel MoS2. Therefore, the gate-electrostatic induced metal-insulator-transition was suggested. At the conference, I will discuss the details of the transport behaviors, gate-potential and temperature dependence of the contact resistance. In addition, I will also discuss potential candidates of other molecules for obtaining doping to TMDCs for going forward the 2D materials-based electronics.
REF: Matsuyama, et al., "Metallic transport in monolayer and multilayer molybdenum disulfides by molecular surface-charge transfer doping", ACS Appl. Mater. Interfaces, 2022, 14, 8163-8170.
(Invited, Digital Presentation) Heterogeneous Integration of Ultrahigh-Κ Single-Crystalline SrTiO3 Membranes for Two-Dimensional Electronics
Authors: Huang Jing-Kai , Wan Yi , Shi Junjie , Zhang Ji , Chiu Ya-Ping , Li Sean , Li Lain-Jong 
Published: November 2022

Even though competitive 2D field-effect transistors (FETs) with the scaled channel dimensions have been demonstrated, it still is a challenge to integrate 2D semiconductors and high-κ dielectrics without deteriorating their interfaces, while decreasing capacitance equivalent thickness (CET) of dielectrics to maintain the gate controllability. In particular, the dielectric/channel interface is one of the predominant factors to affect device performance, including carrier mobility, switching behavior, and drifts of device parameters. This is often caused by the nature of dielectrics used, and the integrating methodologies applied.
Typically, high-κ dielectrics used in silicon technology (i.e., Al2O3 and HfO2) are inherited by 2D FETs. The amorphous nature of these oxides makes the elimination of charge scattering and trapping sites at the dielectric/channel interfaces extremely difficult, not to mention that the direct deposition of dielectrics usually damages the 2D channel and results in poor uniformity in sheer thickness. Some interfacial passivation layers and processes have been developed, but they lead to thickening overall CET instead. Alternative approaches with the crystalline dielectric materials such as multilayer hBN and epitaxial calcium fluoride (CaF2), whose surfaces are well-constructed and atomic-flat, have demonstrated the competitive advantages of crystalline dielectric over the conventional amorphous oxides in spite of relatively lower κ values.
Here, we demonstrate ultra-scaled 2D FETs with desirable sub-1 nm CET through heterogeneous integration of monolayer CVD MoS2 and quasi-2D single-crystalline SrTiO3 membranes, where the optimized SrTiO3 gate dielectrics exhibit a low gate leakage (J
leak < 10-2 A/cm2 at 2.5 MV/cm). Typical transistors manifest good reliability and competitive performance characteristics, including steep subthreshold swings (SS) down to ~70 mV dec-1 and ON/OFF current ratios up to 107, matching low-power specifications suggested by the latest International Roadmap for Devices and Systems (IRDS). In addition, the van der Waals (vdW) interface between quasi-2D dielectrics and 2D semiconductors moderates the unfavorable fringing-induced barrier lowering (FIBL) effect occurring in ultra-scaled Si transistors with very high-κ dielectrics, which broadens the dielectric selection in 2D electronics for future technology node.
Nano-Pattern Oxidation of WSe2
Via Block Copolymer Self-Assembly for Highly Responsive Homojunction Phototransistors
Authors: Kang Miae , Kim Kihyun , Bang Joona , Kim Jihyun 
Published: November 2022

Tungsten diselenide (WSe2), one of the two-dimensional (2D) materials, has emerged as a promising optoelectric candidate because of its thickness dependent bandgap, large optical absorption coefficient, good air stability and high carrier mobility. In addition, the electrical properties of the ambipolar WSe2 could be tuned through the electrostatic doping by the gate modulation. However, the low photo responsivity is a critical problem of WSe2-based optoelectric devices. To overcome this limitation, several approaches have been suggested such as stacking different 2D materials and coating with quantum dots. But these conventional methods were focused on the formation of heterojunctions, which requires complicated alignment process and leads to unavoidable defects and residues. Thus, the novel ways to build homojuction should be investigated for fabricating devices with a clean interface in a simple process.
In this work, block copolymer (BCP) was used to prepare hexagonally packed cylinder nano-template as an oxidation mask for UV/ozone treatment, which resulted in numerous nanoscale homojunctions on WSe2. To fabricate the mask with hexagonally packed cylinders, asymmetric poly (styrene-block-methyl methacrylate) (PS-b-PMMA) was spin-coated. After thermal annealing for self-assembly, PMMA was selectively removed by reactive ion etching. UV/ozone treatment, one of the oxidation methods of the WSe2, leads to the formation of the the tungsten oxide (WOX) with high electron affinity and induces a p-doping effect. By using BCP as an oxidation mask, the only region of the WSe2 under the removed PMMA blocks could be converted into WOX.
The responsivity of the nano-pattern oxidized WSe2 phototransistor manifests a dramatic change depending on the applied gate bias. The device exhibited a responsivity (532 nm, 8.515 mW/cm2) of 27.5 mA/W under applied gate bias of 0 V. However, under the gate bias of +60 V, the device showed an enhanced responsivity of 155.2 mA/W, as strong p-n junctions were induced. In conclusion, the nano-pattern oxidized WSe2 phototransistor presents increased responsivity (155.2 mA/W), external quantum efficiency (36.3%) and faster response time than the pristine WSe2.
This work demonstrates that the responsivity of the WSe2 phototransistor can be improved though well-established perpendicular BCP and optimized by effective modulation of gate bias. By implementing homojunctions on the WSe2
via the nano-pattern oxidation method, this work greatly expands the potential applications of 2D TMDs materials for next-generation nanoscale optoelectronic devices.
(Invited) Wireless Healthcare Flexible Sensor System with Comfortable and Precise Monitoring
Authors: Takei Kuniharu 
Published: November 2022

Daily continuous health condition monitoring is now of great interests using multi-functional flexible sensors. In particular, vital signals from skin are the most convenient way to measure continuously data collections during daily life. For this purpose, flexible sensor sheets allow it to detect multiple information from skin precisely due to conformable covering over skin surface. To realize this platform, multiple developments including flexible sensors, wireless system, and potential application are required. In this talk, I introduce a wireless multiple sensor sheet system with multiple printed flexible sensors such as skin perspiration, respiration, electrocardiogram etc. The system makes a feedback alarm if abnormal human condition signals are detected. Furthermore, to monitor the vital signals precisely and comfortably even under activity such as walking and running, device architecture is also discussed.
Although a lot of researches and developments are still required for practical application, these studies may help to open a door for the next step of flexible electronics.
(Excellent Student Presentation Award) Triboelectrification Induced Self-Powered Microbial Inactivation with Nanowire-Enhanced Localized Electric Field
Authors: Kim Young-Jun , Kim Sang-Woo 
Published: November 2022

Air-transmitted pathogens may lead to severe epidemics (e.g., COVID-19) showing huge threats to public health. Inactivation of the pathogenic microbes in the air is an essential process, whereas the feasibility of existing air disinfection technologies has encountered obstacles including only achieving physical separation but no inactivation, obvious pressure drops, and energy intensiveness. Here we report a rapid disinfection method for inactivating air-transmitted bacteria and viruses using the nanowire-enhanced localized electric field to damage the outer structures of microbes.[1] This air disinfection system is driven by a triboelectric nanogenerator that converts mechanical vibration to electricity effectively and achieves self-powered. Assisted by a rational design for the accelerated charging and trapping of microbes, this self-powered air disinfection system promotes the microbial transport and achieves high performance: >99.99% microbial inactivation within 0.025s in a fast airflow (2 m/s) while only causing low pressure drops (<24 Pa). This rapid, self-powered air disinfection method may fill the urgent need for the air-transmitted microbial inactivation to protect public health.
References

Liu, X. Xie, W. Zhao, N. Liu, P. A. Maraccini, L. M. Sassoubre, A. B. Boehm, Y. Cui, Nano Letters 13, 4288-4293 (2013)