Bulletin of the American Physical Society
APS March Meeting 2017
Volume 62, Number 4
Monday–Friday, March 13–17, 2017; New Orleans, Louisiana
Session F32: Optoelectronic Devices from 2D MaterialsFocus
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Sponsoring Units: DMP Chair: Scott Crooker, LANL Room: 295 |
Tuesday, March 14, 2017 11:15AM - 11:51AM |
F32.00001: Nanostructured materials for broadband light detection Invited Speaker: Paola Barbara Graphene and other atomically thin materials like transition metal dichalcogenides have recently emerged as versatile building blocks for optoelectronics and light detection. For a gapless material like graphene, light absorption occurs in a wide energy range, including ultraviolet, visible, telecom and terahertz radiation, a region of the electromagnetic spectrum where highly sensitive detection is notoriously difficult. Light absorption in graphene causes a large increase in electron temperature, making it an ideal material for hot-electron bolometers. Here we show that graphene nanostructured into quantum dots yields hot electron bolometers with extraordinary performance for broadband photodetection, with a design that is easily scalable and suitable for detector arrays. A. El Fatimy, R. L. Myers-Ward, A. K. Boyd, K. M. Daniels, D. K. Gaskill and P. Barbara, Nature Nanotechnology 11, 335-338 (2016) [Preview Abstract] |
Tuesday, March 14, 2017 11:51AM - 12:03PM |
F32.00002: Origin of Improved Optical Quality of Monolayer MoS2 Grown on Nitride Substrates Yi Wan, Hui Zhang, Yu Ye, Lun Dai Monolayer molybdenum disulphide (MoS2), a 2D semiconductor with remarkable optical and electrical properties, has been in the spotlight recently. In this work, we realize a high-yield, simple method to grow MoS2 on hexagonal boron nitride (h-BN) flakes, which are relatively inert, expected to be free of charged surface states and dangling bonds. We find that the MoS2 on h-BN exhibits enhanced photoluminescence (PL). We draw the conclusion that the enhanced PL intensities originate probably from a weak doping effect from h-BN substrate, rather than the optical interference effect. Moreover, we successfully synthesized MoS2 on gallium nitride (GaN) substrates. The MoS2 grown on GaN shows an obvious PL peak centered around 1.88 eV, indicates that MoS2 grown on GaN suffers scarcely from strain effect which originates from the contraction mismatch during a cooling process from the high growth temperature to room temperature, due to the relatively small discrepancy in the coefficients of thermal expansion between sample and substrate. Polarization-resolved PL spectroscopy shows that MoS2 grown on GaN possess a high degree of circular polarization, even at room temperature. [Preview Abstract] |
Tuesday, March 14, 2017 12:03PM - 12:15PM |
F32.00003: High External Quantum Efficiency in van der Waals Heterostructures for Ultrathin Photovoltaics Joeson Wong, Deep Jariwala, Kevin Tat, Giulia Tagliabue, Artur Davoyan, Michelle Sherrott, Harry Atwater High external radiative efficiency and high external quantum efficiency are prerequisites for an efficient photovoltaic cell. In transition metal dichalcogenides (TMDCs), previous work has demonstrated that near-unity external radiative efficiency is possible through superacid passivation. Yet, near-unity external quantum efficiency has remained elusive. In this work, we experimentally demonstrate that high external quantum efficiencies (\textgreater 50{\%}) are possible in vertical van der Waals heterostructures consisting of graphene, tungsten diselenide, and molybdenum disulfide, on metallic substrates. We achieve near-unity absorption in ultrathin (\textless 15 nm) transition metal dichalcogenides by employing non-trivial phase shifts at the TMDC/metal interface. We show that the use of both graphene and a PN junction geometry leads to an enhancement in the internal quantum efficiency, a measure of the carrier collection efficiency. Moreover, the internal quantum efficiency is shown to exhibit exciton resonances with peak efficiencies \textgreater 70{\%}. In summary, our results presented here will serve as design considerations and principles towards achieving near-unity external quantum efficiency in van der Waals materials. [Preview Abstract] |
Tuesday, March 14, 2017 12:15PM - 12:27PM |
F32.00004: Photo-Detection on Narrow-Bandgap High-Mobility 2D Semiconductors Adam Charnas, Gang Qiu, Yexin Deng, Yixiu Wang, Yuchen Du, Lingming Yang, Wenzhuo Wu, Peide Ye Photo-detection and energy harvesting device concepts have been demonstrated widely in 2D materials such as graphene, TMDs, and black phosphorus. In this work, we demonstrate anisotropic photo-detection achieved using devices fabricated from hydrothermally grown narrow-bandgap high-mobility 2D semiconductor. Back-gated FETs were fabricated by transferring the 2D flakes onto a Si/SiO$_{2}$ substrate and depositing various metal contacts across the flakes to optimize the access resistance for optoelectronic devices. Photo-responsivity was measured and mapped by slightly biasing the devices and shining a laser spot at different locations of the device to observe and map the resulting photo-generated current. Optimization of the Schottky barrier height for both n and p at the metal-2D interfaces using asymmetric contact engineering was performed to improve device performance. [Preview Abstract] |
Tuesday, March 14, 2017 12:27PM - 12:39PM |
F32.00005: Polarization induced optical and electrical control of 2D materials by ferroelectrics Zainab Zafar, Yumeng You Integration of 2D semiconductors with ferroelectrics can provide a route towards control of polarization-switching by piezoelectric effect, allowing the realization of exciting features of next-generation optoelectronic devices. However, a fundamental understanding of spectroscopic investigation based on ferroelectric switching in ferroelectric/2D heterostructures remains elusive. Here, we demonstrate mechanical writing of nanoscale domains in ferroelectric thin film coupled with 2D materials, facilitated by piezoresponse force microscope (PFM). We propose the use of typical Raman/PL imaging to predict the effect of phase change of ferroelectric on 2D materials. Mechanical writing not only controls the local doping region, but also tunes the transport properties of the channel, as confirmed by its electrical characterization. By Raman/PL spectroscopy, we have identified the domain pattern of different polarizations in terms of amplitude modification of thin ferroelectric and possible shifts in wavenumber/energy of the emission peaks of 2D materials. Therefore, the sensitivity of spectroscopic imaging well corroborates the efficacy of mechanical writing for synthesizing ferroelectric gated 2D devices. [Preview Abstract] |
Tuesday, March 14, 2017 12:39PM - 12:51PM |
F32.00006: A MoTe2 based light emitting diode and photodetector for silicon photonic integrated circuits. Ya-Qing Bie, M. Heuck, G. Grosso, M. Furchi, Y. Cao, J. Zheng, E. Navarro-Moratalla, L. Zhou, T. Taniguchi, K. Watanabe, J. Kong, D. Englund, P. Jarillo-Herrero A key challenge in photonics today is to address the interconnects bottleneck in high-speed computing systems. Silicon photonics has emerged as a leading architecture, partly because many components such as waveguides, interferometers and modulators, could be integrated on silicon-based processors. However, light sources and photodetectors present continued challenges. Common approaches for light source include off-chip or wafer-bonded lasers based on III-V materials, but studies show advantages for directly modulated light sources. The most advanced photodetectors in silicon photonics are based on germanium growth which increases system cost.~The emerging two dimensional transition metal dichalcogenides (TMDs) offer a path for optical interconnects components that can be integrated with the CMOS processing by back-end-of-the-line processing steps. Here we demonstrate a silicon waveguide-integrated light source and photodetector based on a p-n junction of bilayer MoTe$_{\mathrm{2}}$, a TMD semiconductor with infrared band gap. The state-of-the-art fabrication technology provides new opportunities for integrated optoelectronic systems. [Preview Abstract] |
Tuesday, March 14, 2017 12:51PM - 1:03PM |
F32.00007: Plasma enhanced ultrastable self-powered visible-blind deep ultraviolet photodetector based on atomically thin boron nitride sheets Peter Xianping Feng, Manuel Rivera, Rafael Velazquez, Ali Aldalbahi We extend our work on the use of digitally controlled plasma deposition technique to synthesize high quality boron nitride nanosheets (BNNSs). The nanoscale morphologies and layered growth characteristics of the BNNSs were characterized using scanning electron microscope, transmission electron microscopy, and atomic force microscopy. The experimental data indicated each sample consists of multiple atomically thin, highly transparent BNNSs that overlap one another with certain orientations. Purity and structural properties were characterized by Raman scattering, XRD, FTIR and XPS. Based on these characterizations, 2D BNNSs based self-powered, visible blind deep UV detectors were designed, fabricated, and tested. The bias, temperature, and humidity effects on the photocurrent strength were investigated. A significant increase of signal-to-noise ratio after plasma treatment was observed. The fabricated photodetectors presented exceptional properties: a very stable baseline and a high sensitivity to weak intensities of radiation in both UVC and UVB range while remaining visible-blind, a high signal-to-noise ratio, and excellent repeatability even when the operating temperature was up to 400 0C. The shift in cutoff wavelength was also observed. [Preview Abstract] |
Tuesday, March 14, 2017 1:03PM - 1:15PM |
F32.00008: Broadband Photovoltaic Detectors based on an Atomically Thin Heterostructure. Mingsheng Long, Erfu Liu, Peng Wang, Anyuan Gao, Hui Xia, Weida Hu, Baigeng Wang, Feng Miao Van der Waals junctions of two-dimensional materials with an atomically sharp interface open up unprecedented opportunities to design and study functional heterostructures. However, many important optoelectronic applications, such as broadband photodetection, are severely hindered by their limited spectral range and reduced light absorption. Here, we present a p-g-n heterostructure formed by sandwiching graphene with a gapless bandstructure and wide absorption spectrum in an atomically thin p-n junction to overcome these major limitations. We have successfully demonstrated a MoS$_{\mathrm{2}}$-graphene-WSe$_{\mathrm{2\thinspace }}$heterostructure for broadband photodetection in the visible to short-wavelength infrared range at room temperature that exhibits competitive device performance, including a specific detectivity of up to 10$^{\mathrm{11}}$ Jones in the near-infrared region. Our results pave the way toward the implementation of atomically thin heterostructures for broadband and sensitive optoelectronic applications. References: M. S. Long \textit{et al.}, Nano Lett. \textbf{16}, 2254 (2016). [Preview Abstract] |
Tuesday, March 14, 2017 1:15PM - 1:27PM |
F32.00009: Ultrasensitive near-infrared photodetectors based on graphene-MoTe$_{\mathrm{2}}$-graphene vertical van der Waals heterostructure Kun Zhang, Yu Ye, Lun Dai Two-dimensional (2D) materials have rapidly established themselves as exceptional building blocks for optoelectronic applications, due to their unique properties and atomically thin nature. Nevertheless, near-infrared (NIR) photodetectors based on layered 2D semiconductors are rarely realized. In this work, we fabricate graphene-MoTe$_{\mathrm{2}}$-graphene vertical vdWs heterostructure by a facile and reliable site controllable transfer method, and apply it for photodetection from visible to the NIR wavelength range. Compared to the 2D semiconductor based photodetectors reported thus far, the graphene-MoTe$_{\mathrm{2}}$-graphene photodetector has superior performance, including high photoresponsivity (110 mA W$^{\mathrm{-1}}$ at 1064 nm and 205 mA W$^{\mathrm{-1}}$ at 473 nm), high external quantum efficiency (\textit{EQE}, 12.9{\%} at 1064 nm and 53.8{\%} at 473 nm), rapid response and recovery processes (rise time of 24 $\mu $s, fall time of 46 $\mu $s under 1064 nm illumination), and free from an external source-drain power supply. The all-2D-materials heterostructure has promising applications in future novel high responsivity, high speed and flexible NIR devices. [Preview Abstract] |
Tuesday, March 14, 2017 1:27PM - 1:39PM |
F32.00010: Graphene-MoS$_{2}$ Heterojunctions for High-Speed Opto-electronics Jason Horng, Alex Wang, Danqing Wang, Alexander Shengzhi Li, Feng Wang Heterostructures consisting of two-dimensional materials has drawn significant attention in different research fields owning to their novel electronic states and potential applications. Transmitting information with transition metal dichalcogenides(TMDC) electro-optical modulator switch interconnect is of great interest for technological applications. However, their high-speed applications have been slowed by their intrinsically high resistivity as well as the difficulties in making optimized metal contacts. Here, we present a new strategy by using graphene as a tunable contact to two-dimensional semiconductors to explore possible applications in high-speed opto-electronics. We will present an optical study to provide better understanding of band alignment in graphene/MoS$_{2}$ heterostructures and a demonstration of high-speed opto-electronics based on these heterostructures. The result shows the new scheme could have potential in both opto-modulators and optical sensing applications. [Preview Abstract] |
Tuesday, March 14, 2017 1:39PM - 1:51PM |
F32.00011: Direct growth of high quality 2D materials-based metal-semiconductor-metal photodiodes Sudiksha Khadka, Miles Lindquists, Thushan Wickramasinghe, Ruhi Thorat, Shrouq Aleithan, Martin Kordesch, Eric Stinaff Metal-semiconductor-metal photodiodes fabricated using a scalable method, where lithographically defined interdigitated electrodes of bulk molybdenum serve as the growth template for producing self-contacted, as-grown two-dimensional (2D) materials-based devices will be presented. Measurements of first generation devices show photo responsivity of \textasciitilde 1 A/W at a source-drain voltage of 1.5 V, which is a few orders of magnitude larger than the values reported under similar measurement conditions. Time resolved measurements show fast responses on the order of \textasciitilde 25 us, faster than previously reported values by a factor of three. We will present details on the device growth and characterization including the most current results after optimization. We will also discuss the effects of various processing and passivation techniques on the performance. This original process, using bulk metallic patterns, results in as-grown, self-forming, electrical contact to the monolayer material, providing a simple, scalable, and reproducible method for creating as-grown two-dimensional materials-based devices with broad implications for basic research and industrial applications. [Preview Abstract] |
Tuesday, March 14, 2017 1:51PM - 2:03PM |
F32.00012: 2D Semiconductors for Valley-Polarized LEDs and Photodetectors Ting Yu The recently discovered two-dimensional (2D) semiconductors, such as transitional-metal-dichalcogenide monolayers, have aroused great interest due to the underlying quantum physics and the appealing optoelectronic applications like atomically thin light-emitting diodes (LEDs) and photodetectors. On the one hand, valley-polarized electroluminescence and photocurrent from such monolayers have not caused enough attention but highly demanded as building blocks for the new generation valleytronic applications. On the other hand, most reports on these devices are based on the mechanically exfoliated small samples. Considering real applications, a strategy which could offer mass-product and high compatibility to the current planar processes is greatly demanded. Large-area samples prepared by chemical vapour deposition (CVD) are perfect candidates towards such a goal. Here, we report electrically tunable valley-polarized electroluminescence and the selective spin--valley-coupled photocurrent in optoelectronic devices based on monolayer WS2 and MoS2 grown by CVD, exhibiting large electroluminescence and photocurrent dichroisms of 81{\%} and 60{\%}, respectively. The controllable valley polarization and emission components of the electroluminescence have been realized by varying electrical injection of carriers. For the observed helicity-dependent photocurrent, the circular photogalvanic effect at resonant excitations has been found to take the dominant responsibility. [Preview Abstract] |
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