Browsing by Author "George, Antony"

Now showing 1 - 5 of 5
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    2D material integrated macroporous electrodes for Li-ion batteries
    (Royal Society of Chemistry, 2017) Gullapalli, Hemtej; Kalaga, Kaushik; Vinod, Soumya; Rodrigues, Marco-Tulio F.; George, Antony; Ajayan, Pulickel M.
    Three-dimensionally structured architectures are known to improve the performance of electrodes used in Li ion battery systems. In addition, integration of select 2D materials into 3D structures, for enhancing both electrical conductivity and electrochemical activity, will prove advantageous. Here a scalable one-step chemical vapor deposition technique is demonstrated for the controlled etching and simultaneous graphene growth on stainless steel substrates resulting in a 3D micro-mesh architecture that is ideal for high rate/high capacity electrodes; the graphene coated 3D stainless steel current collector is used with an MoS2 electrode material for demonstrating high stability and rate capacity in Li-ion batteries.
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    Charge coupled device based on atomically layered van der waals solid state film for opto-electronic memory and image capture
    (2016-08-30) Lei, Sidong; Ge, Liehui; George, Antony; Li, Bo; Vajtai, Robert; Ajayan, Pulickel M.; Rice University; United States Patent and Trademark Office
    An opto-electronic sensor may provide one or more layers of atomically layered photo-sensitive materials. The sensor may include a gate electrode layer, a dielectric layer in contact with the gate electrode layer, and a working media layer that is photo-sensitive deposited on the dielectric layer. The working media layer may provide one or more layers of one or more materials where each of the one or more layers is an atomic layer. The sensor may also include side electrodes in contact with the working media layer.
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    Enabling Ultrasensitive Photo-detection Through Control of Interface Properties in Molybdenum Disulfide Atomic Layers
    (Springer Nature, 2016) Najmaei, Sina; Lei, Sidong; Burke, Robert A.; Nichols, Barbara M.; George, Antony; Ajayan, Pulickel M.; Franklin, Aaron D.; Lou, Jun; Dubey, Madan
    The interfaces in devices made of two-dimensional materials such as MoS2 can effectively control their optoelectronic performance. However, the extent and nature of these deterministic interactions are not fully understood. Here, we investigate the role of substrate interfaces on the photodetector properties of MoS2 devices by studying its photocurrent properties on both SiO2 and self-assembled monolayer-modified substrates. Results indicate that while the photoresponsivity of the devices can be enhanced through control of device interfaces, response times are moderately compromised. We attribute this trade-off to the changes in the electrical contact resistance at the device metal-semiconductor interface. We demonstrate that the formation of charge carrier traps at the interface can dominate the device photoresponse properties. The capture and emission rates of deeply trapped charge carriers in the substrate-semiconductor-metal regions are strongly influenced by exposure to light and can dynamically dope the contact regions and thus perturb the photodetector properties. As a result, interface-modified photodetectors have significantly lower dark-currents and higher on-currents. Through appropriate interfacial design, a record high device responsivity of 4.5 × 103 A/W at 7 V is achieved, indicative of the large signal gain in the devices and exemplifying an important design strategy that enables highly responsive two-dimensional photodetectors.
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    Nanoantenna-Enhanced Light-Matter Interaction in Atomically Thin WS2
    (American Chemical Society, 2015) Kern, Johannes; Trügler, Andreas; Niehues, Iris; Ewering, Johannes; Schmidt, Robert; Schneider, Robert; Najmaei, Sina; George, Antony; Zhang, Jing; Lou, Jun; Hohenester, Ulrich; de Vasconcellos, Steffen Michaelis; Bratschitsch, Rudolf
    Atomically thin transition metal dichalcogenides (TMDCs) are an emerging class of two-dimensional semiconductors. Recently, the first optoelectronic devices featuring photodetection as well as electroluminescence have been demonstrated using monolayer TMDCs as active material. However, the lightﾖmatter coupling for atomically thin TMDCs is limited by their small absorption length and low photoluminescence quantum yield. Here, we significantly increase the lightﾖmatter interaction in monolayer tungsten disulfide (WS2) by coupling the atomically thin semiconductor to a plasmonic nanoantenna. Due to the plasmon resonance of the nanoantenna, strongly enhanced optical near-fields are generated within the WS2ﾠmonolayer. We observe an increase in photoluminescence intensity by more than 1 order of magnitude, resulting from a combined absorption and emission enhancement of the exciton in the WS2monolayer. The polarization characteristics of the coupled system are governed by the nanoantenna. The robust nanoantennaﾖmonolayer hybrid paves the way for efficient photodetectors, solar cells, and light-emitting devices based on two-dimensional materials.
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    Ternary CuIn7Se11: Towards Ultra-Thin Layered Photodetectors and Photovoltaic Devices
    (Wiley, 2014) Lei, Sidong; Sobhani, Ali; Wen, Fangfang; George, Antony; Wang, Qizhong; Huang, Yihan; Dong, Pei; Li, Bo; Najmaei, Sina; Bellah, James; Gupta, Gautam; Mohite, Aditya D.; Ge, Liehui; Lou, Jun; Halas, Naomi J.; Vajtai, Robert; Ajayan, Pulickel
    2D materials have been widely studied over the past decade for their potential applications in electronics and optoelectronics. In these materials, elemental composition plays a critical role in defining their physical properties. Here we report the first successful synthesis of individual high quality CuIn7Se11 (CIS) ternary 2D layers and demonstrate their potential use in photodetection applications. Photoconductivity measurements show an indirect bandgap of 1.1 eV for few-layered CIS, an external quantum efficiency of 88.0 % with 2 V bias across 2 μm channel with and a signal-to-noise ratio larger than 95 dB. By judicious choice of electrode materials, we demonstrate the possibility of layered CIS-based 2D photovoltaic devices. This study examines this ternary 2D layered system for the first time, demonstrating the clear potential for layered CIS in 2D material-based optoelectronic device applications.