bluuebunny/crossref_metadata_2025_split huggingface dataset:
(Invited) Electronics Based on Monolayers
Authors: Li Lain-Jong 
Published: February 2020

Transition metal dichalcogenides (TMDs) are attractive for energy and electronic applications. Our recent success in vapor phase growth of TMD monolayer [1] has stimulated the research in growth and applications [2]. In this presentation, I would discuss the synthesis and characterizations of crystalline MoS2 and WSe2 monolayers. These layer materials can be transferred to desired substrates, making them suitable building blocks for constructing multilayer stacks for various applications [3].

Heterostructures of 2d materials formed by vertical stacking have been realized recently via transfer of their exfoliated flakes, where their properties are dominated by the stacking orientation and strength of interlayer coupling. The method to determine valence band and conduction band alignment for various TMD materials is proposed [4].

Another very attractive structure is lateral heterostructure in which the junction is atomically sharp and the active region can be as narrow as few strings of atoms at the junction areas. This structure offers much easier band offset tuning since materials are spatially separated. The direct growth of such lateral heterostructures will be presented. Preliminary results and perspectives on monolayer electronics shall be discussed.

[1] Adv. Mater. 24, 2320 (2012); ACS Nano 8, 923 (2014). [2] Nat. Chem. 5, 263-275 (2013); Chem. Soc. Rev. (2015) DOI: 10.1039/C4CS00256C. [3] ACS Nano 8, 2951 (2014); ACS Nano 8, 8317 (2014). [4] arXiv:1406.5137 (2015)
(Invited) Enhanced Energy Harvesting Scheme Utilizing Hierarchical Micro/Nanostructures
Authors: Chueh Yu-Lun 
Published: February 2020

In this talk, I will introduce the development of low dimensional nanomaterials in my group and its applications on solar cell and solar energy storage. In the first part of my talk, I will introduce the development of hierarchical nanostructures used to enhance the energy harvesting based on photo-solar and thermal-solar in my group. First, I will report fabrication of a large area Cu(In,Ga)Se2 nanotip arrays (CIGS NTRs) by using one step Ar+ milling process without template. By controlling milling time and incident angles, the length of CIGS NTRs with adjustable tilting orientations can be precisely controlled. The CIGS NTRs have very low reflectance < 0.1 % at incident wavelengths between 300 nm to 1200 nm. Open circuit voltage and short circuit current of CIGS NTRs solar cell were measured to be ~390 mV and ~22.56 mA/cm2, yielding the filling factor and the efficiency of 59 % and 5.2 %, respectively. In contrast to CIGS thin film solar cell with efficiency of 3.2 %, the nanostructured CIGS NTRs can have efficiency enhancement of ~160 % due to the higher light absorption ability because of the nanostructure. In the 2nd part of my talk, an enhanced heat capacity of modified HITEC molten salt by doping of metal NPs will be reported. We encapsulate the Tin alloy into Sn/SiOx core-shell NPs to prevent mixture with salt when operation temperature is higher than the melting point of Tin. The SiOx shell layer can protect the Sn NPs to be oxidized and maintains a melted status during the heat cycles, providing a stable leant heat value of 28.36 J/g. Besides, effective heat capacity of HITEC salt with Sn/SiOx core-shell NPs can be enhanced to be 30 % a mixture percentage of 5 wt%. The merits of this approach show a low-cost and easy way to enhance the thermal properties of current molten salt without complicated manufacturing.
(Invited) Laser Cooling in Semiconductors
Authors: Zhang Jun 
Published: February 2020

Optical irradiation accompanied by spontaneous anti-Stokes emission can lead to cooling of matter, in a phenomenon known as laser cooling. In gaseous matter, an extremely low temperature can be obtained in diluted atomic gases by Doppler cooling; in solid-state materials, laser cooling is achieved by the annihilation of phonons, which are quanta of lattice vibrations, during anti-Stokes luminescence.
Here we will show my studies how to use laser to cool whole semiconductor by using unresolved sideband anti-Stokes luminescence upconversion and how to use laser to cool specific optical phonon vibration by using resolved sideband Raman cooling technique. We demonstrate a net cooling by about 40 kelvin in a semiconductor using group-II–VI cadmium sulphide nanoribbons, or nanobelts, starting from 290 kelvin. We use a pump laser with a wavelength of 514 nanometres, and obtain an estimated cooling efficiency of about 1.3 per cent and an estimated cooling power of 180 microwatts. At 100 kelvin, 532-nm pumping leads to a net cooling of about 15 kelvin with a cooling efficiency of about 2.0 per cent. In resolved sideband regime, we experimentally demonstrate spontaneous Raman cooling and heating of longitudinal optical phonon with a 6.23 THz frequency in polar semiconductor zinc telluride nanobelts. We use the exciton to resonate and assist photo-elastic Raman scattering from LOPs due to the large exciton-LOP coupling. The cooling (heating) is mediated by detuning the laser pump to lower (higher) energy sideband, and spontaneous scattering photon resonates with exciton at anti-Stokes (Stokes) side, that beat and photo-elastically attenuate (enhance) the dipole oscillation of the optical phonon.

References:

J. Zhang, D. H. Li, R. J. Chen, Q. H. Xiong, Laser cooling of a semiconductor by 40 Kelvin, Nature, 493, 504-508 (2013)

J. Zhang, L. C. Kwek, Q. H. Xiong, Resolved Sideband Raman cooling of optical phonons in semiconductor materiaals, Nature Photonics, under review （2015）
(Invited) Operando Measurement of Energy Band Alignment and Built-in Potential in Thin-Film Photovoltaic Devices
Authors: Chen Liwei 
Published: February 2020

The energy band alignment in thin-film or low-dimensional devices is extremely important for charge separation, carrier transport and collection, as well as undesirable recombination. However, experimental determination of the energy level alignment and the quantitative measurement of related parameters, such as the built-in potential (Vbi
), have been difficult to realise, especially under typical operating conditions for the devices. Indirect methods, such as Mott-Schottky analysis, electroabsorption spectroscopy, and dark current density-voltage (J-V) curve fitting, have been applied to measure the Vbi
in solar cells, but the quantitative information has been inaccurate or inconsistent.
Recently, SKPM has been used to image cross sections of solar cells to probe the SP depth profile across multiple layers. The vacuum level (VL) in an energy band structure is defined as the energy of an electron resting right at the surface of a material; thus, the VL alignment within a device can be obtained by multiplying the SP depth profile by a constant, i.e., the electron charge. In principle, this approach offers the advantage of being able to directly visualise the energy band alignment across the device. However, a major obstacle has limited the application of this approach in solar cell research: quantitatively accurate measurements and interpretations have yet to be realised in cross-sectional SKPM studies. Critical parameters for the operating mechanism of solar cells, such as the open-circuit voltage (Voc
) and Vbi
, are often found to be much smaller than expected from J-V characterisation. Overall, the results obtained from cross-sectional SKPM measurements are often uncorrelated with the device performance and J-Vcharacteristics and are thus not applicable for understanding practical devices in their actual operating states.
In this presentation, we address the challenges in quantitative SKPM potentiometry in low-dimensional devices using organic photovoltaic (OPV) cells as model systems. Cross sections of OPV devices are exposed by using ion beam milling; and the SP depth profiles of the OPV device under operating conditions are directly visualised by SKPM imaging on the cross section. The tip/cantilever convolution effect due to finite tip size and cantilever beam cross-talk is identified as the source of the systematic underestimate of SP differences in cross-sectional SKPM measurements. A bias compensation method is developed to obtain quantitative measurements of internal potential difference parameters, such as Voc
, Vtd
and Vbi
, in OPV devices. This method is generally applicable to other thin-film and low-dimensional devices.
Nanopatterned Fiber Based Textile Triboelectiric Nanogenerator
Authors: Seung Wanchul , Kim Sang-Woo 
Published: February 2020

There has been increasing demand for highly efficient portable energy harvesters due to the development and mass consumption of portable electronic devices. Photovoltaic, thermoelectric, piezoelectric and triboelectric energy scavengers have become strong candidates for portable energy harvesters in future self-powered portable electronic device applications.Among these, Triboelectric energy harvesters that can convert mechanical energy into electrical energy have recently attracted attention. Compared to time-constrained photovoltaic, piezoelectric energy harvesters are not limited in time and space because mechanical energy sources such as body movement, heartbeat, blood ﬂow, wind, tide, low-frequency seismic vibrations, and sound from the surrounding environment are prevalent.
In this study, we report the textile based as a substrate for foldable and wearable triboelectric power generators. Nano-size pattened PDMS on the conductive woven fabric substrate by dip-coated method. For practical applications, nano patterned conductive woven fabric based power generator showed the continuous driving of the liquid crystal display screen and light emitting diode successfully. Furthermore, textile based power generator showed high sensitivity acts low applying for of under 1kgf.
The results presented here may create new possibilities for energy harvesting wearable devices, particularly in applications that require wearability and flexibility.
(Invited) Interface and Dielectric Engineering for High-Performance Top-Gated MoS2 Field Effect Transistors
Authors: Zou Xuming , Liao Lei 
Published: February 2020

In recent years, due to the intriguing electrical and optical characteristics, two dimensional layered materials such as MoS2 have attracted tremendous research attention. However, until now, majority of the efforts have been focused on the integration of MoS2 devices in the back- or dual-gated geometry due to the difficulty of compact and conformal top-gated dielectric deposition directly onto the 2-D channel for the realization of high-performance top-gated FETs. In order to integration in TFT circuit for practical application, top-gated FETs with high-k dielectric is necessary. In this regard, interface or dielectric engineering is an important step towards the practical implementation of MoS2 devices with the optimized performance.
Here, we explore the case of interface engineering by utilizing an ultrathin metallic oxide (MgO, Al2O3 and Y2O3) buffer layer inserted between the ALD-HfO2 and MoS2 channel in order to achieve conformal HfO2/MoS2 interfaces with the minimal interface defect density. Exploiting these enhanced gate stack dielectrics, we attain the highest saturation current (526 μA/μm) of any MoS2 transistor reported to date, which is comparable to the same scaled state-of-the-art Si MOSFETs. At the same time, these devices also exhibit the impressive room-temperature mobility (63.7 cm2/V·s), on/off current ratio (>108) and near-ideal sub-threshold slope (SS = 65 mV/decade).
Although Y2O3/HfO2/MoS2 structure improves the device performance greatly, the degradation in mobility is unavoidable. We then further utilize BN as dielectric layer to improve the mobility of top-gated MoS2 device. The mobility value is close to 100 cm2/V·s,
Demonstration of all these suggests that the performance of few-layer MoS2 FETs can reach near intrinsic limits at room temperature along with the proper interface engineering and propose future directions to improve electrical characteristics in layered semiconductors.
(Invited) A Metal Oxide Antifuse-Diode Device
Authors: Kuo Yue 
Published: February 2020

Crystalline metal oxides have been used in various micro and nano electronics and optoelectronics, such as conductors, superconductors, and light emitting devices (LEDs). The amorphous metal oxide dielectric is usually a high-k material suitable for the insulation purpose. The doped metal oxide, such as the Zr-doped HfO2 (ZrHfO), high-k thin film has many advantageous material and electrical properties, such as the high crystallization temperature, low interface layer thickness in contact with Si, and low interface density of states (1). When nanocrystals are embedded into the high-k metal oxide dielectric thin film, electrons and charges can be stored for a long period of time, which is suitable for the nonvolatile memory application (2). Recently, it was proved by the author’s group that the broad band white light could be emitted from the metal oxide dielectric thin film after the dielectric breakdown due to the thermal excitation of the nano size conductive paths (3). In this talk, a new high-k dielectric based device that shows both antifuse and diode functions is reported. Figure 1 shows a large “programmed” to “unprogrammed” leakage current ratio of 105 is obtained from an original MOS capacitor made of a high-kgate dielectric on a p-type wafer, which fits the antifuse requirement. Figure 2 shows that for a same device in the programmed state, the leakage current increases with the increase of the magnitude of the gate voltage in the negative voltage range. However, the leakage current remains low and changes little over a large range of gate voltage in the positive voltage range, which is similar to the diode behavior. On the other hand, the leakage current-voltage curve of the new device is almost linear while that of the conventional diode follows the exponential relationship. The operation physics, structure, and material properties of the new device will be discussed in detail.

Y. Kuo, J. Lu, S. Chatterjee, J. Yan, H. C. Kim, T. Yuan, W. Luo, J. Peterson, and M. Gardner, “Sub 2 nm Thick Zirconium Doped Hafnium Oxide High-K Gate Dielectrics,” ECS Trans., 1(5), 447-454 (2006).

Y. Kuo, invited, “Nanocrystals Embedded High-k Nonvolatile Memories – bulk film and nanocrystal material effects,” ECS Trans., 53(4), 121-128 (2013).

Y. Kuo, invited, “A Solid State Thin Film Incandescent Light Emitting Device,” Proc. IDEM, 104-107 (2014).

Figure 1
(Invited) Imprinted Functional Nano-Structures for Highly Efficient Photonic Devices
Authors: Lee Heon 
Published: February 2020

Recently, nanoimprint lithography (NIL) has gained great attention as an effective patterning technology in the fields of light emitting diodes (LEDs), solar cells, and other optical devices, because of its simplicity and cost effectiveness. The aim of this research is the development of NIL based direct printing process with an imprint resist containing dispersed various metal oxide (ZnO, TiO2, and ATO) nano-particles. A functional nano pattern can be easily fabricated by this direct printing of functional materials. The properties of substrates, such as transmittance, diffraction, refractive index, and hydrophobicity, was successfully controlled by forming the functional nano-patterns. Finally, the efficiency of optoelectronic devices, such as solar cell and light-emitting diodes was drastically enhanced.
A Controllable and Widely Applicable Electrochemical Anodization Process to Fabricate Porous Anodic Aluminum Oxide Membrane
Authors: Lin Yuanjing , Lin Qingfeng , Liu Xue , Gao Yuan , Fan Zhiyong 
Published: February 2020

Inspired by the versatile applications of porous alumina nanostructures on solar cells, supercapacitors, biosensors, and so forth, research on fabrication of anodized aluminum oxide (AAO) with nanopore structure has achieved substantial advancements. Porous AAO membrane with nanostructures has become one of the most popular template materials for synthesis of a broad range of functional nanostructures such as nanowires, nanopillars, nanotubes, etc. While fabrication of highly ordered nanoporous AAO with tunable geometric features has been widely reported, its growth rate can be easily affected by the fluctuation of parameters such as acid concentration and temperature during the electrochemical anodization process. In order to meet the demand of fabricating AAO with various surface parameters and precise target pore depth control for scientific research and commercial applications, a controllable fabrication process is essential. Here, we developed a method which can implement precise pore depth control of AAO layer during the electrochemical anodization process, via monitoring the integrated charge. This method is applicable in a large voltage range and can be widely applied in fabrication of nanostructure with material such as TiO2and so on.
(Invited) New Electrochemiluminescent Materials for Bioanalysis
Authors: Xu Guobao , Qi Wenjing , Zhang Ling , Liu Xiaoqing , Hu Lianzhe 
Published: February 2020

Electrochemiluminescence (ECL), or electrogenerated chemiluminescence, is light-emitting phenomenon from electrochemical reactions. It has broad applications, such as immunoassays, DNA probe assays, aptasensors, biological study, drug screening, medicine determination, and light-emitting devices. Various ECL systems, such as ruthenium complex, luminol, semiconductor nanocrystals, graphene oxide, and nanoclusters, have been reported. Generally, ECL reactions involve in luminophores, coreactants, and electrode. Electrocatalysts and/or additives are also frequently used. The performance of ECL depends significantly on these materials used [1-2].
We have recently developed various materials to improve ECL performance, such as new coreactants, new luminophores, noble metal nanocrystals, silica nanomaterials, new electrodes. The possible mechanism for enhanced properties are discussed. The analytical applications of some materials were demonstrated. The use of these materials extends applications, improve ECL sensitivity and simplify detection. [3-7].

Acknowledgements

This project was supported by the National Natural Science Foundation of China (No. 21475123 and 21175126).

References

[1] Z. Y. Liu, W. J. Qi, G. B. Xu, Chem. Soc. Rev., 2015, DOI: 10.1039/c5cs00086f.
[2] L. Zhang, W. X. Niu, G. B. Xu, Nano Today, 2012, 7, 586-605.
[3] X. Q. Liu, L. H. Shi, W. X. Niu, H. J. Li, G. B. Xu, Angew. Chem. Int. Ed., 2007, 46, 421-424.
[4] W. J. Qi, Z. Y. Liu, J. P. Lai, W. Y. Gao, X. Y. Liu, M. Xu, G. B. Xu, Chem. Commun., 2014, 50, 8163-8166.
[5] L.Z. Hu, Z. Bian, H. J. Li, S. Han, Y. L. Yuan, L. X. Gao, G. B. Xu, Anal. Chem., 2009, 81, 9807-9811
[6] W. J. Qi, D. Wu, J. M. Zhao, Z. Y. Liu, W. Zhang, L. Zhang, G. B. Xu, Anal. Chem., 2013, 85, 3207.
[7] L. Zhang, W. X. Niu, W. Y. Gao, L. M. Qi, J. P. Lai, J. M. Zhao, G. B. Xu, ACS Nano 2014, 8, 5953–5958.
Cultivation of Rat Nerve Cells on Nanoimprinted Microstructures on Polydimethylsiloxane Sheets
Authors: Koshinuma Eiki , Maenosono Hirotaka , Endo Daisuke , Nishioka Yasushiro 
Published: February 2020

Regenerative medical research has attracted remarkable attention after the development of induced pluripotent stem (iPS) cells [1]. Current focus in this field of research aims at restoring the function of the nervous system after trauma. The transplantation of neural stem cell suspension into an injured area has proven to be an effective treatment method. Several reports related to possible treatments of extensively injured areas and extension of remedy time have been published [2]. However, the shortcoming of this research is mainly associated with the limited ability of the nerve cells to regenerate. Other interesting areas of regenerative medicine are related to the artificial fabrication of the lost human functions such as the nervous system in a laboratory setting [3].
Polydimethylsiloxane (PDMS) films are very flexible and stretchable films and various kinds of micro patterns have been fabricated onto these using microelectromechanical system (MEMS) techniques such as nanoimprinting [4]. Here we report the cultivation of nerve cells on PDMS culture sheets with micro trench structures on a PDMS substrate fabricated using nanoimprinting.　We fabricated micro trench structures with varying widths of 15 and 150 μm and depths of 30 and 60 μm using the nanoimprint technique on a 100 μm thick polydimethylsiloxane culture sheet used as a biocompatible polymer culture sheet. Rat neurons were observed to grow after 3 days selectively within those micro trenches with widths larger than 15 μm, and they were coated with polylysine. Accumulation of glial cells was also observed in the trenches.
References
[1] K. Takahashi and S. Yamanaka, Cell, 126 (2006) 663.
[2] P. Brundin, J. Karlsson, M. Emgård, G. S. Schierle, O. Hansson, A. Petersén, and R. F. Castilho, Cell Transplant., 9 (2000) 179.
[3] R Singhvi, A. Kumar, G. P. Lopez, G. N. Stephanopoulos, D. I. Wang, G. M. Whitesides, and D. E. Ingber. Science, 264 (1994) 696.
[4] M. N. De Silva, R. Desai, and D. J. Odde. Biomed. Microdevices, 6 (2004) 219.
Bridging the Gap - Rediscovering Black Phosphorus As an Anisotropic Layered Material for Electronics and Optoelectronics
Authors: Wang Han 
Published: February 2020

In this talk, I will discuss our recent work in introducing black phosphorus (BP) to the layered-material family as a novel anisotropic 2D material for electronic and optoelectronic applications [1] [2]. Narrow gap BP thin film (0.3 eV in bulk) serendipitously fill the energy space between zero-gap graphene and large-gap TMDCs, making it an promising material for near and mid-infrared optoelectronics [3]. BP thin films show high mobility above 650 cm2/V.s at room temperature along the light effective mass (x) direction, implying its promising potential for high frequency, thin-film electronics. Furthermore, its anisotropic nature within the plane of the layers may allow for the realization of conceptually new electronic and photonic devices impossible in other 2D materials. In the talk, I will also present our work in demonstrating 20 GHz black phosphorus radio-frequency transistors [4]. Our recent progress in characterizing the optical properties of monolayer BP [5] and in achieving large-area synthesis of black phosphorus thin film will also be discussed. I will conclude with remarks on promising future directions of black phosphorus research and how this new material is expected to benefit the next-generation electronics and photonics technologies.

References

[1] X. Ling, H. Wang*, S. Huang, F. Xia, M. Dresselhaus* “The Renaissance of Black Phosphorus” Proceedings of the National Academy of Sciences (PNAS), 112, 15, 4523-4530, 2015. doi: 10.1073/pnas.1416581112.
[2] F. Xia*, H. Wang*, Y. Jia “Rediscovering Black Phosphorus as an Anisotropic Layered Material for Optoelectronics and Electronics” Nature Communications, 5:4458 doi: 10.1038/ncomms5458, 2014.
[4] F. Xia, H. Wang, D. Xiao, M. Dubey, A. Ramasubramaniam “Two-Dimensional Material Nanophotonics” Nature Photonics, 8 (12), 899-907.
[3] H. Wang*, X. Wang, F. Xia*, L, Wang, H. Jiang, Q. Xia, M. Chin, M. Dubey, S.-J. Han “Black Phosphorus Radio Frequency Transistors” Nano Lett., 14 (11), 6424-6429, 2014.
[5] X. Wang, A. M. Jones, K. L. Seyler, V. Tran, Y. Jia, H. Zhao, H. Wang, L. Yang, X. Xu, F. Xia "Highly Anisotropic and Robust Excitons in Monolayer Black Phosphorus" Nature Nanotechnology, published on line, 2015. doi:10.1038/nnano.2015.71.