@article{yu_minhaj_huang_yu_cao_2020, title={In-Plane and Interfacial Thermal Conduction of Two-Dimensional Transition-Metal Dichalcogenides}, volume={13}, ISSN={["2331-7019"]}, DOI={10.1103/PhysRevApplied.13.034059}, abstractNote={We elucidate the dependence of the in-plane and interfacial thermal conduction of two-dimensional (2D) transition-metal dichalcogenide (TMDC) materials (including ${\mathrm{Mo}\mathrm{S}}_{2}$, ${\mathrm{WS}}_{2}$, and ${\mathrm{W}\mathrm{Se}}_{2}$) on the materials' physical features, such as size, layer number, composition, and substrates. The in-plane thermal conductivity k is measured at suspended 2D TMDC materials and the interfacial thermal conductance g is measured at materials supported on substrates, both through Raman thermometry techniques. The thermal conductivity k increases with the radius R of the suspended area following a logarithmic scaling as k\ensuremath{\sim}log(R). k also shows a substantial decrease from monolayer to bilayer, but only changes slightly with a further increase in the layer number. In contrast, the interfacial thermal conductance g has a negligible dependence on the layer number, but g increases with the strength of the interaction between 2D TMDC materials and the substrate, substantially varying among different substrates. The result is consistent with theoretical predictions and clarifies much inconsistence in the literature. This work provides useful guidance for thermal management in 2D TMDC materials and devices.}, number={3}, journal={PHYSICAL REVIEW APPLIED}, author={Yu, Yifei and Minhaj, Tamzid and Huang, Lujun and Yu, Yiling and Cao, Linyou}, year={2020}, month={Mar} }
 @article{ullah_habib_huang_garcia-camara_2019, title={Analysis of the Substrate Effect on the Zero-Backward Scattering Condition of a Cu2O Nanoparticle under Non-Normal Illumination}, volume={9}, ISSN={["2079-4991"]}, DOI={10.3390/nano9040536}, abstractNote={The presence of a substrate is one of the most important limitations of the real application of the directional conditions. These conditions allow the control of the spatial distribution of light scattering of nanoparticles. While the zero-forward condition is quite sensitive to any change of the surrounding medium, like the substrate, the zero-backward scattering seems to be less sensitive and very stable under normal illumination. In this letter, the zero-backward scattering condition was investigated on a homogenous Cu2O spherical subwavelength particle, both theoretically and experimentally. In particular, the influence of the substrate and the impinging direction on the angular distribution of light scattering under this directional condition were studied. We observed that the zero-backward scattering condition was also sensitive to the presence of a substrate beneath when a non-normal illumination was considered. We believe that our finding is quite interesting from a practical point of view and for the real implementation of directional scattering in various applications like cloaking, light-emitting devices, photovoltaic devices, bio-sensing, and many more.}, number={4}, journal={NANOMATERIALS}, author={Ullah, Kaleem and Habib, Muhammad and Huang, Lujun and Garcia-Camara, Braulio}, year={2019}, month={Apr} }
 @article{ullah_liu_huang_farooq_iqbal_garcia camara_2018, title={Imaging the scattering field of a single GaN nanowire}, volume={20}, ISSN={["2040-8986"]}, DOI={10.1088/2040-8986/aae0d1}, abstractNote={In this work, a single gallium nitride (GaN) nanowire has been examined by our previously reported technique parametric indirect microscopic imaging (PIMI). Mapping of the nanoscale scattering signals from GaN nanowire has been achieved with PIMI system. A comparison with classical far field microscopy and FDTD simulations is included to show the relevant differences and the strength of this technique. In PIMI, highly defined modulated illumination, far field variation quantification, and filtering process resolve the nanoscale scattering field distribution in the form of polarization parameters. We believe that our system provides us a platform to understand the physics of these nanoscale scattering fields from optical nanoantennas.}, number={10}, journal={JOURNAL OF OPTICS}, author={Ullah, Kaleem and Liu, Xuefeng and Huang, Lujun and Farooq, Umair and Iqbal, Muhammad Faisal and Garcia Camara, Braulio}, year={2018}, month={Oct} }
 @article{yu_li_huang_barrette_cai_yu_gundogdu_zhang_cao_2017, title={Enhancing Multifunctionalities of Transition-Metal Dichalcogenide Monolayers via Cation Intercalation}, volume={11}, ISSN={1936-0851 1936-086X}, url={http://dx.doi.org/10.1021/ACSNANO.7B04880}, DOI={10.1021/acsnano.7b04880}, abstractNote={We have demonstrated that multiple functionalities of transition-metal dichalcogenide (TMDC) monolayers may be substantially improved by the intercalation of small cations (H+ or Li+) between the monolayers and underlying substrates. The functionalities include photoluminescence (PL) efficiency and catalytic activity. The improvement in PL efficiency may be up to orders of magnitude and can be mainly ascribed to two effects of the intercalated cations: p-doping to the monolayers and reducing the influence of substrates, but more studies are necessary to better understand the mechanism for the improvement in the catalytic functionality. The cation intercalation may be achieved by simply immersing substrate-supported monolayers into the solution of certain acids or salts. It is more difficult to intercalate under the monolayers interacting with substrates stronger, such as as-grown monolayers or the monolayers on 2D material substrates. This result presents a versatile strategy to simultaneously optimize multiple functionalities of TMDC monolayers.}, number={9}, journal={ACS Nano}, publisher={American Chemical Society (ACS)}, author={Yu, Yifei and Li, Guoqing and Huang, Lujun and Barrette, Andrew and Cai, Yong-Qing and Yu, Yiling and Gundogdu, Kenan and Zhang, Yong-Wei and Cao, Linyou}, year={2017}, month={Sep}, pages={9390–9396} }
 @article{yu_yu_huang_peng_xiong_cao_2017, title={Giant Gating Tunability of Optical Refractive Index in Transition Metal Dichalcogenide Monolayers}, volume={17}, ISSN={["1530-6992"]}, DOI={10.1021/acs.nanolett.7b00768}, abstractNote={We report that the refractive index of transition metal dichacolgenide (TMDC) monolayers, such as MoS2, WS2, and WSe2, can be substantially tuned by >60% in the imaginary part and >20% in the real part around exciton resonances using complementary metal-oxide-semiconductor (CMOS) compatible electrical gating. This giant tunablility is rooted in the dominance of excitonic effects in the refractive index of the monolayers and the strong susceptibility of the excitons to the influence of injected charge carriers. The tunability mainly results from the effects of injected charge carriers to broaden the spectral width of excitonic interband transitions and to facilitate the interconversion of neutral and charged excitons. The other effects of the injected charge carriers, such as renormalizing bandgap and changing exciton binding energy, only play negligible roles. We also demonstrate that the atomically thin monolayers, when combined with photonic structures, can enable the efficiencies of optical absorption (reflection) tuned from 40% (60%) to 80% (20%) due to the giant tunability of the refractive index. This work may pave the way toward the development of field-effect photonics in which the optical functionality can be controlled with CMOS circuits.}, number={6}, journal={NANO LETTERS}, author={Yu, Yiling and Yu, Yifei and Huang, Lujun and Peng, Haowei and Xiong, Liwei and Cao, Linyou}, year={2017}, month={Jun}, pages={3613–3618} }
 @article{ni_wang_zhao_ma_xing_yang_huang_lin_zhang_2017, title={Realisation of a humidity sensor based on perfect metamaterial absorber}, volume={49}, number={1}, journal={Optical and Quantum Electronics}, author={Ni, B. and Wang, Z. Y. and Zhao, R. S. and Ma, X. Y. and Xing, Z. Q. and Yang, L. S. and Huang, L. J. and Lin, Y. Y. and Zhang, D. B.}, year={2017} }
 @article{huang_li_gurarslan_yu_kirste_guo_zhao_collazo_sitar_parsons_et al._2016, title={Atomically Thin MoS2 Narrowband and Broadband Light Superabsorbers}, volume={10}, ISSN={["1936-086X"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000381959100030&KeyUID=WOS:000381959100030}, DOI={10.1021/acsnano.6b02195}, abstractNote={We present a combined theoretical and experimental effort to enable strong light absorption (>70%) in atomically thin MoS2 films (≤4 layers) for either narrowband incidence with arbitrarily prespecified wavelengths or broadband incidence like solar radiation. This is achieved by integrating the films with resonant photonic structures that are deterministically designed using a unique reverse design approach based on leaky mode coupling. The design starts with identifying the properties of leaky modes necessary for the targeted strong absorption, followed by searching for the geometrical features of nanostructures to support the desired modes. This process is very intuitive and only involves a minimal amount of computation, thanks to the straightforward correlations between optical functionality and leaky modes as well as between leaky modes and the geometrical feature of nanostructures. The result may provide useful guidance for the development of high-performance atomic-scale photonic devices, such as solar cells, modulators, photodetectors, and photocatalysts.}, number={8}, journal={ACS NANO}, author={Huang, Lujun and Li, Guoqing and Gurarslan, Alper and Yu, Yiling and Kirste, Ronny and Guo, Wei and Zhao, Junjie and Collazo, Ramon and Sitar, Zlatko and Parsons, Gregory N. and et al.}, year={2016}, month={Aug}, pages={7493–7499} }
 @inproceedings{ni_wang_zhao_ma_xing_yang_huang_lin_zhang_2016, title={Humidity sensor based on perfect metamaterial absorber}, booktitle={International conference on numerical simulation of optoelectronic}, author={Ni, B. and Wang, Z. Y. and Zhao, R. S. and Ma, X. Y. and Xing, Z. Q. and Yang, L. S. and Huang, L. J. and Lin, Y. Y. and Zhang, D. B.}, year={2016}, pages={37–38} }
 @article{lin_huang_yu_he_cao_2015, title={Deterministic phase engineering for optical Fano resonances with arbitrary lineshape and frequencies}, volume={23}, ISSN={["1094-4087"]}, DOI={10.1364/oe.23.019154}, abstractNote={We present an approach of deterministic phase engineering that can enable the rational design of optical Fano resonances with arbitrarily pre-specified lineshapes. Unlike all the approaches previously used to design optical Fano resonances, which fall short of designing the resonances with arbitrary lineshapes because of the lack of information for the optical phases involved, we develop our approach by capitalizing on unambiguous knowledge for the phase of optical modes. Optical Fano resonances arise from the interference of photons interacting with two optical modes with substantially different quality factors. We find that the phase difference of the two modes involved in optical Fano resonances is determined by the eigenfrequency difference of the modes. This allows us to deterministically engineer the phase by tuning the eigenfrequency, which may be very straightforward. We use dielectric grating structures as an example to illustrate the notion of deterministic engineering for the design of optical Fano resonances with arbitrarily pre-specified symmetry, linewidth, and wavelengths.}, number={15}, journal={OPTICS EXPRESS}, author={Lin, Jiao and Huang, Lujun and Yu, Yiling and He, Sailing and Cao, Linyou}, year={2015}, month={Jul}, pages={19154–19165} }
 @article{yu_hu_su_huang_liu_jin_purezky_geohegan_kim_zhang_et al._2014, title={Equally Efficient Interlayer Exciton Relaxation and Improved Absorption in Epitaxial and Nonepitaxial MoS2/WS2 Heterostructures}, volume={15}, ISSN={1530-6984 1530-6992}, url={http://dx.doi.org/10.1021/nl5038177}, DOI={10.1021/nl5038177}, abstractNote={Semiconductor heterostructures provide a powerful platform to engineer the dynamics of excitons for fundamental and applied interests. However, the functionality of conventional semiconductor heterostructures is often limited by inefficient charge transfer across interfaces due to the interfacial imperfection caused by lattice mismatch. Here we demonstrate that MoS(2)/WS(2) heterostructures consisting of monolayer MoS(2) and WS(2) stacked in the vertical direction can enable equally efficient interlayer exciton relaxation regardless the epitaxy and orientation of the stacking. This is manifested by a similar 2 orders of magnitude decrease of photoluminescence intensity in both epitaxial and nonepitaxial MoS(2)/WS(2) heterostructures. Both heterostructures also show similarly improved absorption beyond the simple superimposition of the absorptions of monolayer MoS(2) and WS(2). Our result indicates that 2D heterostructures bear significant implications for the development of photonic devices, in particular those requesting efficient exciton separation and strong light absorption, such as solar cells, photodetectors, modulators, and photocatalysts. It also suggests that the simple stacking of dissimilar 2D materials with random orientations is a viable strategy to fabricate complex functional 2D heterostructures, which would show similar optical functionality as the counterpart with perfect epitaxy.}, number={1}, journal={Nano Letters}, publisher={American Chemical Society (ACS)}, author={Yu, Yifei and Hu, Shi and Su, Liqin and Huang, Lujun and Liu, Yi and Jin, Zhenghe and Purezky, Alexander A. and Geohegan, David B. and Kim, Ki Wook and Zhang, Yong and et al.}, year={2014}, month={Dec}, pages={486–491} }
 @article{yu_huang_cao_2014, title={Semiconductor Solar Superabsorbers}, volume={4}, ISSN={["2045-2322"]}, DOI={10.1038/srep04107}, abstractNote={Understanding the maximal enhancement of solar absorption in semiconductor materials by light trapping promises the development of affordable solar cells. However, the conventional Lambertian limit is only valid for idealized material systems with weak absorption and cannot hold for the typical semiconductor materials used in solar cells due to the substantial absorption of these materials. Herein we theoretically demonstrate the maximal solar absorption enhancement for semiconductor materials and elucidate the general design principle for light trapping structures to approach the theoretical maximum. By following the principles, we design a practical light trapping structure that can enable an ultrathin layer of semiconductor materials, for instance, 10 nm thick a-Si, absorb > 90% sunlight above the bandgap. The design has active materials with one order of magnitude less volume than any of the existing solar light trapping designs in literature. This work points towards the development of ultimate solar light trapping techniques.}, journal={SCIENTIFIC REPORTS}, author={Yu, Yiling and Huang, Lujun and Cao, Linyou}, year={2014}, month={Feb} }
 @article{huang_yu_cao_2013, title={General Modal Properties of Optical Resonances in Subwavelength Nonspherical Dielectric Structures}, volume={13}, ISSN={["1530-6992"]}, DOI={10.1021/nl401150j}, abstractNote={Subwavelength dielectric structures offer an attractive low-loss alternative to plasmonic materials for the development of resonant optics functionalities such as metamaterials and optical antennas. Nonspherical-like rectangular dielectric structures are of the most interest from the standpoint of device development due to fabrication convenience. However, no intuitive fundamental understanding of the optical resonance in nonspherical dielectric structures is available, which has substantially delayed the development of dielectric resonant optics devices. Here, we elucidate the general fundamentals of the optical resonance in nonspherical subwavelength dielectric structures with different shapes (rectangular or triangular) and dimensionalities (1D nanowires or 0D nanoparticles). We demonstrate that the optical properties of nonspherical dielectric structures are dictated by the eigenvalue of the structure's leaky modes. Leaky modes are defined as optical modes with propagating waves outside the structure. We also elucidate the dependence of the modal eigenvalue on physical features of the structure. The eigenvalue shows scale invariance with respect to the size of the structure, weak dependence on the refractive index, but linear dependence on the size ratio of different sides of the structure. We propose a modified Fabry-Perot model to account for the linear dependence. The knowledge of leaky modes, including the role in optical responses and the dependence on physical features, can serve as a powerful guide for the rational design of devices with desired optical resonances. It may open up a pathway to design devices with functionality that has not been explored due to the lack of intuitive understanding, for instance, imaging devices able to sense incident angle or superabsorbing photodetectors.}, number={8}, journal={NANO LETTERS}, author={Huang, Lujun and Yu, Yiling and Cao, Linyou}, year={2013}, month={Aug}, pages={3559–3565} }