bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermoelectric Properties of Ge-Rich GeSn Films Grown on Insulators
Authors: Kurosawa Masashi , Liu Kun , Izawa Momoka , Tsunoda Isao , Zaima Shigeaki 
Published: February 2020

Thermoelectric generator has attracted attention because of their ability to recover waste heat with converting it to electricity. The energy conversion efficiency is related to the thermoelectric figure of merit Z, expressed as Z = S2σ/κ, where σ and κ is electrical and thermal conductivities, respectively, and S is the Seebeck coefficient. Consequently, in order to achieve a high Z value, the material must possess a unique combination of electrical and thermal properties, i.e., metal-like high σ and glass-like low κ. In our previous study on electrical and thermal properties of a Ga-doped Ge0.929Sn0.071 thin film grown on Ge(001), it was revealed that simultaneous realization of a high σ (6.5×102 S/cm) and a low κ (2.0 Wm-1K-1) by the incorporations of the Sn and Ga atoms into Ge matrix [1]. Very recently, Uchida et al. [2] has reported heat transport property of polycrystalline GeSn (poly-GeSn) films on SiO2, together with the carrier transport property, to assess self-heating effect of the poly-GeSn channel thin-film transistors. Here, they showed a relatively lower κ of 5–9 Wm-1K-1 for poly-Ge1-xSnx (x<0.14) compared with that for bulk Ge (60 Wm-1K-1) [3]. These results are quite beneficial in the field of Ge-based thermoelectric generator. However, the thermoelectric properties of GeSn films have not been entirely understood. It is therefore, in the present study, we aim to reveal the thermoelectric properties of the Ge-rich poly-Ge1-xSnx films grown by solid phase crystallization. Doping effects in poly-Ge1-xSnxon the thermoelectric properties will be discussed.

Acknowledgments

The authors would like to thank Drs. Hiroshi Onoda and Yoshiki Nakashima of Nissin Ion Equipment Co., Ltd. for providing the opportunity to use ion implanters. This work was partially supported by a Grant-in-Aid for Scientific Research (S) (Grant No. 26220605) of the JSPS and PRESTO from JST.

References

[1] M. Kurosawa, M. Fukuda, K. Takahashi, M. Sakashita, O. Nakatsuka, and S. Zaima, “Thermophysical characterizations of Ge1-xSnx epitaxial layers aiming for thermoelectric device,” 9th International Conference on Silicon Epitaxy and Heterostructures (ICSI-9), Montreal, Canada, 4.4.1, May 21, 2015.
[2] N. Uchida, T. Maeda, R. R. Lieten, S. Okajima, Y. Ohishi, R. Takase, M. Ishimaru, and J.-P. Locquet, Appl. Phys. Lett. 107, 232105 (2015).
[3] C. J. Glassbrenner and G. A. Slack, Phys. Rev. 134, A1058 (1964).
Integration of High Quality III-V Materials on Si Using the Aspect-Ratio-Trapping Technique
Authors: Zhou Xuliang , Li Shiyan , Pan Jiaoqing 
Published: February 2020

III-V compound semiconductor materials grown on elemental semiconductor substrates have attracted much attention due to their mobility and direct bandstructure. And the III-V/Si system could combine the advantages of both material systems. The growth of high quality III-V thin films on Si (or Ge) is the first crucial step for III-V high-mobility or optical devices. However, The large lattice mismatch between III-V materials and Si is the main challenge for its integration on large sized Si wafers. Recently, the aspect-ratio trapping (ART) technique offers an elegant and cost effective solution for integrating III-V materials on the Si wafer.
We report the selective area growth of III-V materials in “V-shaped” trenches on Si (001) substrates via metal-organic chemical vapor deposition (MOCVD).High quality GaAs thin films were achieved using a two-step growth process and the aspect ratio trapping method.In addition, high quality InP and InAs film was grown in trenches with a GaAs buffer layer. Material quality was confirmed by scanning electron microscope (SEM), transmission electron microscopy (TEM) and high resolution x-ray diffraction (HRXRD).This approach shows that these III-V materials could be high mobility channels for future CMOS technology node.
We also report a InGaAs/InP multi-quantum-well growth in nanoscale V-shaped trenches on Si (001) substrate was studied using the aspect ratio trapping method. A high quality GaAs/InP buffer layer with two convex {111} B facets was selectively grown to promote the highly uniform, single-crystal ridge InP/InGaAs multi-quantum-well structure growth. Material quality was confirmed by transmission electron microscopy and room temperature micro-photoluminescence measurements. This approach shows great promise for the fabrication of photonics devices like nanolasers on Si substrate.
Direct Wafer Bonding of SiC-SiC at Room Temperature by SAB Method
Authors: Mu Fengwen , Iguchi Kenichi , Nakazawa Haruo , Takahashi Yoshikazu , Fujino Masahisa , Suga Tadatomo 
Published: February 2020

The efficiency improvement of power devices is of significance because the energy saving and prevention of global warming are urgent issues. However, it is difficult to realize further improvement by using the conventional silicon (Si) because of its limited physical properties. Silicon carbide (SiC) has attracted considerable attention owing to its superior properties such as wider band gap, higher dielectric breakdown field, higher thermal conductivity, higher stability in a harsh environment, and so on [1-3]. With successive breakthroughs in aspects of material technology and device fabrication such as 6-inch 4H-SiC wafer being and various devices becoming commercially available, SiC power devices will be widely used in the foreseeable future [4]. As a result, the fabrication and integration technologies of SiC power device in mass production will be very important. Wafer bonding is a widely used technology for device fabrication and integration, while studies about directly wafer bonding of SiC-SiC at low temperature are still hardly. Therefore, directly wafer bonding of SiC-SiC at room temperature by SAB method was investigated in this work.
In the directly wafer bonding process, the two SiC wafers surfaces were firstly activated by argon fast-atom-beam (Ar-FAB), followed by directly contacted in UHV bonding chamber under a certain pressure. After bonding, a scanning acoustic microscopy (SAM) was used to inspect the voids of the bonded wafer, followed by blade insertion method to test the bonding strength. In addition, the bonding interfaces were analyzed by high-resolution transmission electron microscopy (HR-TEM) and energy-dispersive X-ray spectroscopy (EDX).

References

M. B. J. Wijesundara, and R. G. Azevedo, Silicon carbide microsystems for harsh environments (Springer, New York, 2011), pp. 15.

Y. Hijikata, Physics and Technology of Silicon Carbide Devices, (InTech, Rijeka, 2012) pp. 181.

T. Kimoto, Symp. VLSI Technology, 2010, p. 9.

H. Okumura, MRS. Bull. 40, 439 (2015).
Novell Plating Processes for Silicon Based Pixel Detectors
Authors: Fritz Mathias , Nieland Sabine , Wittig Tobias , Bund Andreas 
Published: February 2020

New generation silicon detectors produced in Thuringia (Germany) will play an important role in the future, during the upgrade phase of the Large Hadron Collider (LHC) at the CERN nuclear research center. Such detectors are used for monitoring radioactive reactions during the collision of highly accelerated positron radiations produced in large scale experiments like ATLAS (A
Toroidal LHC ApparatuS) or CMS (Compact-Muon-Solenoid).
The development of the new detectors aims at a functional improvement that will bring an enhanced resistance against radiation damage. At the same time, the surface reengineering for an increased active surface should address also important cost related aspects.
This paper will discuss recent results from the authors' labs on the development of such novel sensors. The aim is a full understanding and coverage of the complete production process for the sensor modules. An important challenge to be addressed is the development of low cost metallisation procedures for the silicon detectors that do not require lithographic steps. Especially promising are extreme small and round surfaces of about 10 µm diameter distributed over the entire detector surface with a contact pitch of 50 µm that would add up to several thousand contacts and a high contact density. Given the special structure of the detector surface, electric current can be generated by incoming electromagnetic radiation, e.g. light. This current can be used in a light-induced metallization process of the front side contacts. We will present results from a light-induced plating process involving nickel and tin. The suitability of this layer system for subsequent bonding processes will also be discussed.
Light Gated Zinc Tin Oxide Thin Film Transistor Fabricated Via Solution Process
Authors: Wang I-Wen , Li Jeng-Ting , Chen Jen-Sue 
Published: February 2020

Zinc tin oxide (ZTO) is a transparent semiconductor based on earth-abundant elements. While most oxide semiconductor films were previously fabricated by vacuum-based deposition techniques, solution processes are increasingly popular due the lower cost and feasibility for large area deposition. In this work, ZTO films prepared by a solution route have been applied as the active semiconductor layer in a thin film transistor (TFT) with SiO2 or Al2O3 dielectrics. With thickness less than 10 nm, the ZTO film exhibits a good field-effect mobility of ~10 cm2/Vs, small subthreshold slope of ~0.5 V/decade and high on/off current ratio of ~107.
With light illumination of 405 nm wavelength and power density of 5 mW/cm2, the light sensitivity is in the order of 106 for the ID-off region and is less than 10 for the ID-on region. The light responsibility of ZTO TFT reaches around 2.5 and the maximum external quantum efficiency is 8.
Furthermore, to see the light gating effect, the ZTO TFT is operated without applying gate voltage but under light illumination (405 nm wavelength) of various power densities. At a drain voltage of 0.5 V, the drain current increases sharply from 0.3 μA to 12.1 μA when the light power density increases from 0.03 mW/cm2 to 0.25 mW/cm2. The increment of drain current becomes gradual for power intensity greater than 0.25 mW/cm2 (from 13.4 μA to 16.3 μA for light power density from 0.5 mW/cm2 to 5 mW/cm2). As a result, the solution-processed ZTO TFT can be gated with light illumination, in addition to the voltage gating mode. This finding will broaden the suitability of ZTO TFT in optoelectronic and optical communication applications.
(Invited) Diluted Magnetic Monolayer MoS2 Synthesis, Characterization and Device Applications
Authors: Xiang Bin , Zhao Benliang , Fan Yaohui , Wang Wenhui , Yang Lei 
Published: February 2020

Keywords: Two dimensional; Monolayer; CVD; Spintronics; Spin injection
Recently, monolayer MoS2 has attracted intensive interests because of its special properties. MoS2-based field effect transistor exhibits a carrier mobility of 900 cm2 V-1 s-1 and an on/off ratio larger than 108.[1] However, its non-magnetic property has retarded its applications in the quantum devices. Diluted magnetic semiconductors have been extensively studied, as it bridges the ferromagnetic and semiconductor properties.[2] It shows a variety of new physical phenomena and functionalities.[3] There is few reports on diluted magnetic monolayer MoS2 semiconductors. In this paper, we design a rational synthesis of diluted magnetic monolayer MoS2 by a simple chemical vapor deposition method. By characterizing the structural, chemical composition, magnetic property, magnetic transport, we confirm the as-synthesized sample is single phase of diluted magnetic monolayer MoS2 with promising ferromagnetic property. We probe the mechanism of the ferromagnetic behavior observed in the as-grown diluted magnetic monolayer MoS2. The spin-injection efficiency is investigated by studying the injected relaxation and lift time. Our results would open up a new path way to develop the future flexible quantum devices and quantum computers.
References:
1. Radisavljevic, B. et al. Single-layer MoS2 transistors. Nature Nanotech. 2011, 6, 147-150.
2. Dietl, T., et al., Rev. Mod. Phys., 2014, 86, 187-251.
3. Dietl, T., Nat. Mater., 2010, 9, 965-974.
(Invited) Facile Horizontal GaAs Nanowire Schottky Solar Cells with Record High Efficiency
Authors: Han Ning , Ho Johnny C 
Published: February 2020

Nowadays, it is still technological challenging to fabricate solar cells with the high efficiency and low cost aimed for the third generation photovoltaics as well as for powering nano-devices by smart power supply. In this study, highly crystalline, long and dense GaAs nanowires (NWs) are easily synthesized on amorphous SiO2/Si substrates in the solid source chemical vapor deposition (CVD) system. And the single GaAs NWs are fabricated into Au-Al asymmetric Schottky contact solar cells [2] by a simple ultraviolet photolithography process. The NW synthesis avoids the use of expensive single crystalline epitaxial substrates such as GaAs(111)B used in metal-organic (MO) CVD or molecular beam epitaxy (MBE) methods [1], and device fabrication gets rid of the complicated p-i-n structures complementation. Besides these low-cost advantages of the NW synthesis and device fabrication, the horizontal NW solar cell show a record high efficiency of ~17% under air mass 1.5 global (AM 1.5G) illumination as shown in Figure 1. This produces another record in addition to the vertically aligned p-i-n GaAs NW solar cells previously reported (40%), in which the superior photovoltaic performance is attributed to the light concentrating effect of NWs with diameter in the order of light wavelength [3]. Moreover, the GaAs NWs can be printed onto glass and plastics to enhance the output power as well as provide the transparent and flexible solar cells as shown in Figure 1. All these results show the promising prospect of the high quality GaAs NWs synthesis in low cost solid source CVD system, and the highly efficient photovoltaic applications in the simple Schottky contact configuration.
1 N. Han, J. J. Hou, F. Y. Wang, S. Yip, Y. T. Yen, Z. X. Yang, G. F. Dong, T. Hung, Y. L. Chueh and J. C. Ho, ACS Nano 7 (2013) 9138.
2 N. Han, Z. Yang, F. Wang, G. Dong, S. Yip, X. Liang, T. F. Hung, Y. Chen and J. C. Ho, ACS Appl. Mater. Interfaces 7 (2015) 20454.
3 P. Krogstrup, H. I. Jorgensen, M. Heiss, O. Demichel, J. V. Holm, M. Aagesen, J. Nygard and A. F. I. Morral, Nat. Photonics 7 (2013) 306.

Figure 1
(Invited) Understanding the Energy Band Alignment in Inverted Organic Thin-Film Photovoltaic Devices
Authors: Chen Liwei 
Published: February 2020

The energy band alignment in thin-film and low-dimensional devices is extremely important. However, experimental determination or theoretical prediction of the energy level alignment has been difficult to realize, especially under typical operating conditions.
Following a recent breakthrough in our group, where SKPM technique was employed to image the vacuum level profile across the depth direction of an operando organic PV device with a conventional stacking structure, here we present the vacuum level alignment measurement on an inverted structure OPV device. Previously, there had been conflicting reports on the built-in field and the device operation polarity. In this talk, we will present a comprehensive understanding of the energy level alignment in inverted structure OPVs, and how the measured parameters can be adopted in numerical modeling of the device physics.
(Invited) Automatic Particle and Cell Detection and Manipulation in a Microfluidic Chip
Authors: Song Yongxin 
Published: February 2020

This presentation reports our researches on the automatic detection and manipulation of particles and cells in a microfluidic chip. A differential resistive pulse sensor is developed and employed to continually detect and sizing particles. Due to the noise cancelling effect, the S/N is greatly improved. As a result, detection of 220nm particles was achieved with a relative larger sensing gate.
Automatic particle and cell sorting based on their size differences was also reported in this presentation. The RPS sensor was used to sizing the particles or cells. The detected RPS signals were used to automatically trigger the sorting process. Due to the high sensitivity of the RPS sensor, 1um sorting resolution was achieved. This technology can also be used to manipulating cells at a single cell level.

Keywords: Resistive Pulse Sensor, Detection and sorting, single cell levelAbstract

This presentation reports our researches on the automatic detection and manipulation of particles and cells in a microfluidic chip. A differential resistive pulse sensor is developed and employed to continually detect and sizing particles. Due to the noise cancelling effect, the S/N is greatly improved. As a result, detection of 220nm particles was achieved with a relative larger sensing gate.
Automatic particle and cell sorting based on their size differences was also reported in this presentation. The RPS sensor was used to sizing the particles or cells. The detected RPS signals were used to automatically trigger the sorting process. Due to the high sensitivity of the RPS sensor, 1um sorting resolution was achieved. This technology can also be used to manipulating cells at a single cell level.
Keywords: Resistive Pulse Sensor, Detection and sorting, single cell level
Heat Transfer Enhancement By Elastic Turbulence in a Micro Curvilinear Channel
Authors: Zhang Hong Na , Li Dong Yang , Li Xiao Bin , Li Feng Chen 
Published: February 2020

With the increasing level of microelectronic techniques, such as MEMS, the effective heat transfer become crucial to their performance. Genernally, the flow in microscale behaves laminar because of the extremely low Reynolds number (Re), which results in very low heat transfer effeciceny. So far, an increasingly efforts have been paid to develop techiniques to improve the heat transfer therein. As is well known in the conventional scale, flow instabilities and turbulence could significantly promote the mixing and heat transfer. Therefore, a great deal of efforts have been paid to to perturb the low Reynolds number flows in order to increase the contact interfaces between fluids with different temperature in microchannel. For example, some efforts are paid to design and utilize specially designed microchannel to excite the unstable flow motion. Another alternative way is to adopt different kinds of working fluid such as nano-fluid, non-Newtonian fluid and so forth. The viscoelastic fluid, a kind of Non-Newtonian fluid, shows nontrivial flow phenomena such as die swell effect (Barus effect), rod climbing effect (Weissenberg effect), Kaye effect, tubeless siphon effect, etc. Moreover, it has been proven that purely elastic flow instabilities or elastic turbulence is possible to be induced under inertialess or creeping flow conditions. This provides another efficient way to realize heat transfer enhancement, which is also the focus of present paper.
In this paper, we carried out experimental and numerical investigations on the heat transfer characteristics of viscoelastic fluid and Newtonian fluid in three dimensional (3D) curvilinear microchannel. For the experiments, microelectronics manufacturing technology was taken to fabricate microchips. Platinum films were embedded in a Polydimethyl-siloxane (PDMS) microchannel in order to measure micro heater and channel wall temperature. The polymer solutions (PAAM) were the chosen viscoelastic fluid and sucrose solutions (Newtonian fluid) were used for comparison. For the numerical simulation, the log-conformation algorithm were implemented into the open source software OpenFOAM in order to simulate the viscoelastic flow at high Weissenberg number. Before simulating the viscoelastic fluid flow passing through the target channel, the numerical solver was firstly validated by two benchmark problems i.e., flow around a cylinder and passing a cross-slot by comparing the obtained dimensionless drag coefficient and flow patterns with those in the existing literatures. Combing the experimental and numerical results, the present identified the heat transfer enhancement by the occurrence of elastic instability and turbulence in a curved microchannel.
Viscoelastic Slip Velocity for Microscale Electrokinetic Flows
Authors: Joo Sang W. , Saadat Amir , Khomami Bamin 
Published: February 2020

Microscale electrokinetic flows are often analysed neglecting the full details of the dynamics within the electric double layer (EDL) ajacent to solid boundaries. The high-shear velocity profile within the EDL is simplified by the Helmholtz-Smolukowski velocity, imposed in leu of the noslip boundary condition. For Newtonian fluid this slip boundary condition can be a convenient tool for economical simulation of more complex phenomena. Viscoelastic fluids are ubiquitous in micro devices, and so the slip velocity generalised for non-Newtonian fluids is needed.
In this study, analytical solution extending the Helmholtz-Smolukowski velocity to viscoelastic electroosmotic flow is presented for the first time based on conservation laws. By using the Phan–Thien Tannar (PTT) constitutive model, explicit dependence of viscoelastic rheological parameters, including the relaxation time, the slip parameter and the extensibility parameter, on the slip velocity on the edge of electrical double layer (EDL) is revealed. This report will be instrumental in providing a deep insight into the dynamics of the viscoelastic fluids subject to electrokinetic forces and in making the long-sought micro-scale approximation of complex viscoelastic flow possible.
High Performance Organic Photovoltaics with Transparent Oxide Interlayer
Authors: Kim Hyeok 
Published: February 2020

Organic photovoltaics (OPVs) have remarkable attention due to their cost-effective, simple process and large area manufacturing as energy sources for printed and flexible electronics. In this talk, we demonstrate that inorganic interlayer can prominently improve the performance of inverted polymer solar cells with the mixture of [6,6]-phenyl C71-butyric acid methyl ester (PC70BM) and diverse donors, such as poly[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b]dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]-thiophenediyl(PTB7) and many more.
One of the common technique to enhance the electrical and optical properties of inorganic thin film layer has been suggested with doping of various metals for oxide inorganic films, such as ZnO, TiO2 and other metal oxides. It was recently reported that metal doping of ZnO thin film such as Li, Al, or Ga is an effective way to modify the grain size and orientation of ZnO crystallites. It may predominantly be effective as the structural, optical and electrical properties enhancer. Here, we adopted various metal dopants to inverted OPVs in ZnO and TiO2 interlayers. The doped ZnO film with a number of dopants, thus, such as Al, Ga, In, Li and Cd, was prepared by sol-gel spin coating and the optimized doping concentration appeared for each dopant. As suggested as one of the most highly improved efficiency, In-doped ZnO (IZO) film with 6 at. % of In concentration was intercalated between the ITO electrode and the active layer. As a result, the power conversion efficiency approaches 9 % exceedingly. Moreover, the underlying mechanism was revealed as the suppressed absorption and facilitated electron extraction of inorganic interlayer with metal doping through the first principles calculations and finite difference time domain (FDTD) optical simulation.