InSe

/Tag: InSe

Liquid-phase exfoliated indium-selenide flakes and their application in hydrogen evolution reaction. (arXiv:1903.08967v1 [cond-mat.mtrl-sci])

2019-03-22T02:29:27+00:00March 22nd, 2019|Categories: Publications|Tags: , , |

Single- and few-layered InSe flakes are produced by the liquid-phase exfoliation of beta-InSe single crystals in 2-propanol, obtaining stable dispersions with a concentration as high as 0.11 g/L. Ultracentrifugation is used to tune the morphology, i.e., the lateral size and thickness of the as-produced InSe flakes. We demonstrate that the obtained InSe flakes have maximum lateral sizes ranging from 30 nm to a few um, and thicknesses ranging from 1 to 20 nm, with a max population centred at ~ 5 nm, corresponding to 4 Se-In-In-Se quaternary layers. We also show that no formation of further InSe-based compounds (such as In2Se3) or oxides occurs during the exfoliation process. The potential of these exfoliated-InSe few-layer flakes as a catalyst for hydrogen evolution reaction (HER) is tested in hybrid single-walled carbon nanotubes/InSe heterostructures. We highlight the dependence of the InSe flakes morphologies, i.e., surface area and thickness, on the HER performances achieving best efficiencies with small flakes offering predominant edge effects. Our theoretical model unveils the origin of the catalytic efficiency of InSe flakes, and correlates the catalytic activity to the Se vacancies at the edge of the flakes.

Published in: "arXiv Material Science".

Pressure-controlled Structural Symmetry Transition in Layered InSe. (arXiv:1903.04315v1 [physics.optics])

2019-03-12T02:29:26+00:00March 12th, 2019|Categories: Publications|Tags: , |

Structural symmetry of crystals plays important roles in physical properties of two-dimensional (2D) materials, particularly in the nonlinear optics regime. It has been a long-term exploration on the physical properties in 2D materials with various stacking structures, which correspond to different structural symmetries. Usually, the manipulation of rotational alignment between layers in 2D heterostructures has been realized at the synthetic stage through artificial stacking like assembling Lego bricks. However, the reconfigurable control of translational symmetry of crystalline structure is still challenging. High pressure, as a powerful external control knob, provides a very promising route to circumvent this constraint. Here, we experimentally demonstrate a pressure-controlled symmetry transition in layered InSe. The continuous and reversible evolution of structural symmetries can be in-situ monitored by using the polarization-resolved second harmonic generation (SHG) spectroscopy. As pressure changes, the reconfigurable symmetry transition of the SHG pattern from three-fold rotational symmetry to mirror symmetry was experimentally observed in a layered InSe samples and was successfully explained by the proposed interlayer-translation model. This opens new routes towards potential applications of manipulating crystal symmetry of 2D materials.

Published in: "arXiv Material Science".

Low‐Voltage Operational, Low‐Power Consuming, and High Sensitive Tactile Switch Based on 2D Layered InSe Tribotronics

2019-02-23T22:31:56+00:00February 23rd, 2019|Categories: Publications|Tags: , |

A highly tactile‐sensitive (106 signal modulation) tribotronic transistor with a low operating voltage (0.1 V) and low power consumption is developed. The tribotronic transistor consists of the vertical combination of an In‐doped InSe transistor and triboelectric nanogenerator. This work demonstrates the promise of 2D material–based tribotronics for use in sensors and intelligent systems with low power consumption. Abstract Electronics based on layered indium selenide (InSe) channels exhibit promising carrier mobility and switching characteristics. Here, an InSe tribotronic transistor (denoted as w/In InSe T‐FET) obtained through the vertical combination of an In‐doped InSe transistor and triboelectric nanogenerator is demonstrated. The w/In InSe T‐FET can be operated by adjusting the distance between two triboelectrification layers, which generates a negative electrostatic potential that serves as a gate voltage to tune the charge carrier transport behavior of the InSe channel. Benefiting from the surface charging doping of the In layer, the w/In InSe T‐FET exhibits high reliability and sensitivity with a large on/off current modulation of 106 under a low drain–source voltage of 0.1 V and external frictional force. To demonstrate its function as a power‐saving tactile sensor, the w/In InSe T‐FET is used to sense “INSE” in Morse code and power on a light‐emitting diode. This work reveals the promise of 2D material–based tribotronics for use in nanosensors with low power consumption as well as in intelligent systems.

Published in: "Advanced Functional Materials".

Low‐Voltage Operational, Low‐Power Consuming, and High Sensitive Tactile Switch Based on 2D Layered InSe Tribotronics

2019-02-10T14:34:26+00:00February 10th, 2019|Categories: Publications|Tags: , |

A highly tactile‐sensitive (106 signal modulation) tribotronic transistor with a low operating voltage (0.1 V) and low power consumption is developed. The tribotronic transistor consists of the vertical combination of an In‐doped InSe transistor and triboelectric nanogenerator. This work demonstrates the promise of 2D material–based tribotronics for use in sensors and intelligent systems with low power consumption. Abstract Electronics based on layered indium selenide (InSe) channels exhibit promising carrier mobility and switching characteristics. Here, an InSe tribotronic transistor (denoted as w/In InSe T‐FET) obtained through the vertical combination of an In‐doped InSe transistor and triboelectric nanogenerator is demonstrated. The w/In InSe T‐FET can be operated by adjusting the distance between two triboelectrification layers, which generates a negative electrostatic potential that serves as a gate voltage to tune the charge carrier transport behavior of the InSe channel. Benefiting from the surface charging doping of the In layer, the w/In InSe T‐FET exhibits high reliability and sensitivity with a large on/off current modulation of 106 under a low drain–source voltage of 0.1 V and external frictional force. To demonstrate its function as a power‐saving tactile sensor, the w/In InSe T‐FET is used to sense “INSE” in Morse code and power on a light‐emitting diode. This work reveals the promise of 2D material–based tribotronics for use in nanosensors with low power consumption as well as in intelligent systems.

Published in: "Advanced Functional Materials".

Low‐Voltage Operational, Low‐Power Consuming, and High Sensitive Tactile Switch Based on 2D Layered InSe Tribotronics

2019-02-09T10:32:56+00:00February 9th, 2019|Categories: Publications|Tags: , |

A highly tactile‐sensitive (106 signal modulation) tribotronic transistor with a low operating voltage (0.1 V) and low power consumption is developed. The tribotronic transistor consists of the vertical combination of an In‐doped InSe transistor and triboelectric nanogenerator. This work demonstrates the promise of 2D material–based tribotronics for use in sensors and intelligent systems with low power consumption. Abstract Electronics based on layered indium selenide (InSe) channels exhibit promising carrier mobility and switching characteristics. Here, an InSe tribotronic transistor (denoted as w/In InSe T‐FET) obtained through the vertical combination of an In‐doped InSe transistor and triboelectric nanogenerator is demonstrated. The w/In InSe T‐FET can be operated by adjusting the distance between two triboelectrification layers, which generates a negative electrostatic potential that serves as a gate voltage to tune the charge carrier transport behavior of the InSe channel. Benefiting from the surface charging doping of the In layer, the w/In InSe T‐FET exhibits high reliability and sensitivity with a large on/off current modulation of 106 under a low drain–source voltage of 0.1 V and external frictional force. To demonstrate its function as a power‐saving tactile sensor, the w/In InSe T‐FET is used to sense “INSE” in Morse code and power on a light‐emitting diode. This work reveals the promise of 2D material–based tribotronics for use in nanosensors with low power consumption as well as in intelligent systems.

Published in: "Advanced Functional Materials".

Charged impurity scattering in two-dimensional materials with ring-shaped valence bands: GaS, GaSe, InS, and InSe

2019-02-08T14:33:54+00:00February 8th, 2019|Categories: Publications|Tags: |

Author(s): Protik Das, Darshana Wickramaratne, Bishwajit Debnath, Gen Yin, and Roger K. LakeThe singular density of states and the two Fermi wave vectors resulting from a ring-shaped or “Mexican hat” valence band give rise to unique trends in the charged impurity scattering rates and charged impurity limited mobilities. Ring-shaped valence bands are common features of many monolayer and fe…[Phys. Rev. B 99, 085409] Published Fri Feb 08, 2019

Published in: "Physical Review B".

AsP/InSe Van der Waals Tunneling Heterojunctions with Ultrahigh Reverse Rectification Ratio and High Photosensitivity

2019-02-04T08:37:19+00:00February 4th, 2019|Categories: Publications|Tags: , |

AsP/InSe van der Waals tunneling heterojunctions are demonstrated. The tunneling heterojunctions show an ultrahigh reverse rectification ratio over 107 and an ultralow forward current below picoampere. This device can be operated as an ultrasensitive broadband photodetector with an ultrahigh light on/off ratio of 1 × 107 and a high detectivity over 1 × 1012 Jones in the visible wavelength range. Abstract Van der Waals heterojunctions made of 2D materials offer competitive opportunities in designing and achieving multifunctional and high‐performance electronic and optoelectronic devices. However, due to the significant reverse tunneling current in such thin p–n junctions, a low rectification ratio along with a large reverse current is often inevitable for the heterojunctions. Here, a vertically stacked van der Waals heterojunction (vdWH) tunneling device is reported consisting of black arsenic phosphorus (AsP) and indium selenide (InSe), which shows a record high reverse rectification ratio exceeding 107 along with an unusual ultralow forward current below picoampere and a high current on/off ratio over 108 simultaneously at room temperature under the proper band alignment design of both the Schottky junction and the heterojunction. Therefore, the vdWH tunneling device can function as an ultrasensitive photodetector with an ultrahigh light on/off ratio of 1 × 107, a comparable responsivity of around 1 A W−1, and a high detectivity over 1 × 1012 Jones in the visible wavelength range. Furthermore, the device exhibits a clear photovoltaic effect and shows a spectral detection capability up to 1550 nm. The work sheds light on developing future electronic and

Published in: "Advanced Functional Materials".

AsP/InSe Van der Waals Tunneling Heterojunctions with Ultrahigh Reverse Rectification Ratio and High Photosensitivity

2019-02-02T22:33:06+00:00February 2nd, 2019|Categories: Publications|Tags: , |

AsP/InSe van der Waals tunneling heterojunctions are demonstrated. The tunneling heterojunctions show an ultrahigh reverse rectification ratio over 107 and an ultralow forward current below picoampere. This device can be operated as an ultrasensitive broadband photodetector with an ultrahigh light on/off ratio of 1 × 107 and a high detectivity over 1 × 1012 Jones in the visible wavelength range. Abstract Van der Waals heterojunctions made of 2D materials offer competitive opportunities in designing and achieving multifunctional and high‐performance electronic and optoelectronic devices. However, due to the significant reverse tunneling current in such thin p–n junctions, a low rectification ratio along with a large reverse current is often inevitable for the heterojunctions. Here, a vertically stacked van der Waals heterojunction (vdWH) tunneling device is reported consisting of black arsenic phosphorus (AsP) and indium selenide (InSe), which shows a record high reverse rectification ratio exceeding 107 along with an unusual ultralow forward current below picoampere and a high current on/off ratio over 108 simultaneously at room temperature under the proper band alignment design of both the Schottky junction and the heterojunction. Therefore, the vdWH tunneling device can function as an ultrasensitive photodetector with an ultrahigh light on/off ratio of 1 × 107, a comparable responsivity of around 1 A W−1, and a high detectivity over 1 × 1012 Jones in the visible wavelength range. Furthermore, the device exhibits a clear photovoltaic effect and shows a spectral detection capability up to 1550 nm. The work sheds light on developing future electronic and

Published in: "Advanced Functional Materials".

AsP/InSe Van der Waals Tunneling Heterojunctions with Ultrahigh Reverse Rectification Ratio and High Photosensitivity

2019-01-31T10:37:50+00:00January 31st, 2019|Categories: Publications|Tags: , |

AsP/InSe van der Waals tunneling heterojunctions are demonstrated. The tunneling heterojunctions show an ultrahigh reverse rectification ratio over 107 and an ultralow forward current below picoampere. This device can be operated as an ultrasensitive broadband photodetector with an ultrahigh light on/off ratio of 1 × 107 and a high detectivity over 1 × 1012 Jones in the visible wavelength range. Abstract Van der Waals heterojunctions made of 2D materials offer competitive opportunities in designing and achieving multifunctional and high‐performance electronic and optoelectronic devices. However, due to the significant reverse tunneling current in such thin p–n junctions, a low rectification ratio along with a large reverse current is often inevitable for the heterojunctions. Here, a vertically stacked van der Waals heterojunction (vdWH) tunneling device is reported consisting of black arsenic phosphorus (AsP) and indium selenide (InSe), which shows a record high reverse rectification ratio exceeding 107 along with an unusual ultralow forward current below picoampere and a high current on/off ratio over 108 simultaneously at room temperature under the proper band alignment design of both the Schottky junction and the heterojunction. Therefore, the vdWH tunneling device can function as an ultrasensitive photodetector with an ultrahigh light on/off ratio of 1 × 107, a comparable responsivity of around 1 A W−1, and a high detectivity over 1 × 1012 Jones in the visible wavelength range. Furthermore, the device exhibits a clear photovoltaic effect and shows a spectral detection capability up to 1550 nm. The work sheds light on developing future electronic and

Published in: "Advanced Functional Materials".

AsP/InSe Van der Waals Tunneling Heterojunctions with Ultrahigh Reverse Rectification Ratio and High Photosensitivity

2019-01-31T10:37:47+00:00January 31st, 2019|Categories: Publications|Tags: , |

AsP/InSe van der Waals tunneling heterojunctions are demonstrated. The tunneling heterojunctions show an ultrahigh reverse rectification ratio over 107 and an ultralow forward current below picoampere. This device can be operated as an ultrasensitive broadband photodetector with an ultrahigh light on/off ratio of 1 × 107 and a high detectivity over 1 × 1012 Jones in the visible wavelength range. Abstract Van der Waals heterojunctions made of 2D materials offer competitive opportunities in designing and achieving multifunctional and high‐performance electronic and optoelectronic devices. However, due to the significant reverse tunneling current in such thin p–n junctions, a low rectification ratio along with a large reverse current is often inevitable for the heterojunctions. Here, a vertically stacked van der Waals heterojunction (vdWH) tunneling device is reported consisting of black arsenic phosphorus (AsP) and indium selenide (InSe), which shows a record high reverse rectification ratio exceeding 107 along with an unusual ultralow forward current below picoampere and a high current on/off ratio over 108 simultaneously at room temperature under the proper band alignment design of both the Schottky junction and the heterojunction. Therefore, the vdWH tunneling device can function as an ultrasensitive photodetector with an ultrahigh light on/off ratio of 1 × 107, a comparable responsivity of around 1 A W−1, and a high detectivity over 1 × 1012 Jones in the visible wavelength range. Furthermore, the device exhibits a clear photovoltaic effect and shows a spectral detection capability up to 1550 nm. The work sheds light on developing future electronic and

Published in: "Advanced Functional Materials".

Observation of ballistic avalanche phenomena in nanoscale vertical InSe/BP heterostructures. (arXiv:1901.10392v1 [cond-mat.mtrl-sci])

2019-01-30T02:29:29+00:00January 30th, 2019|Categories: Publications|Tags: , , , |

Initiating impact ionization of avalanche breakdown essentially requires applying a high electric field in a long active region, hampering carrier-multiplication with high gain, low bias and superior noise performance. Here we report the observation of ballistic avalanche phenomena in sub-MFP scaled vertical indium selenide (InSe)/black phosphorus (BP) heterostructures. The heterojunction is engineered to avalanche photodetectors (APD) and impact ionization transistors, demonstrating ultra-sensitive mid-IR light detection (4 {mu}m wavelength) and ultra-steep subthreshold swing, respectively. These devices show an extremely low avalanche threshold (<1 volt), excellent low noise figures and distinctive density spectral shape. Further transport measurement evidences the breakdown originals from a ballistic avalanche phenomenon, where the sub-MFP BP channel enables both electrons and holes to impact-ionize the lattice and abruptly amplify the current without scattering from the obstacles in a deterministic nature. Our results shed light on the development of advanced photodetectors and efficiently facilitating carriers on the nanoscale.

Published in: "arXiv Material Science".

Evidence of Direct Electronic Band Gap in two-dimensional van der Waals Indium Selenide crystals. (arXiv:1901.08481v1 [cond-mat.mes-hall])

2019-01-25T04:30:37+00:00January 25th, 2019|Categories: Publications|Tags: , |

Metal mono-chalcogenide compounds offer a large variety of electronic properties depending on chemical composition, number of layers and stacking-order. Among them, the InSe has attracted much attention due to the promise of outstanding electronic properties, attractive quantum physics, and high photo-response. Metal mono-chalcogenide compounds offer a large variety of electronic properties depending on chemical composition, number of layers and stacking-order. Among them, the InSe has attracted much attention due to the promise of outstanding electronic properties, attractive quantum physics, and high photo-response. Precise experimental determination of the electronic structure of InSe is sorely needed for better understanding of potential properties and device applications. Here, combining scanning tunneling spectroscopy (STS) and two-photon photoemission spectroscopy (2PPE), we demonstrate that InSe exhibits a direct band gap of about 1.25 eV located at the Gamma point of the Brillouin zone (BZ). STS measurements underline the presence of a finite and almost constant density of states (DOS) near the conduction band minimum (CBM) and a very sharp one near the maximum of the valence band (VMB). This particular DOS is generated by a poorly dispersive nature of the top valence band, as shown by angle resolved photoemission spectroscopy (ARPES) investigation. technologies. In fact, a hole effective mass of about m/m0 = -0.95 gammaK direction) was measured. Moreover, using ARPES measurements a spin-orbit splitting of the deeper-lying bands of about 0.35 eV was evidenced. These findings allow a deeper understanding of the InSe electronic properties underlying the potential of III-VI semiconductors for electronic and photonic

Published : "arXiv Mesoscale and Nanoscale Physics".

Out-of-plane orientation of luminescent excitons in atomically thin indium selenide flakes. (arXiv:1901.06719v1 [cond-mat.mes-hall])

2019-01-23T04:30:52+00:00January 23rd, 2019|Categories: Publications|Tags: , |

Van der Waals materials offer a wide range of atomic layers with unique properties that can be easily combined to engineer novel electronic and photonic devices. A missing ingredient of the van der Waals platform is a two-dimensional crystal with naturally occurring out-of-plane luminescent dipole orientation. Here we measure the far-field photoluminescence intensity distribution from InSe samples of varying thicknesses down to the quantum confined regime and demonstrate that, in contrast to other two-dimensional semiconductors such as WSe$_2$ and MoSe$_2$, layered InSe flakes sustain luminescent excitons with an intrinsic out-of-plane orientation. We perform ab-initio calculations of the electronic band structure of bulk and two-dimensional InSe to reveal the dipole orientation is due to the $p_z$ orbital nature of the intra-layer electronic states unique to the the III-VI semiconductor family. These results, combined with the highly tunable optical response from the near-infrared to the visible spectrum and high quality electronic transport properties, position layered InSe as a promising semiconductor for novel optoelectronic devices – in particular hybrid integrated photonic chips which exploit the out-of-plane dipole orientation.

Published : "arXiv Mesoscale and Nanoscale Physics".

Indirect to direct gap crossover in two-dimensional InSe revealed by ARPES. (arXiv:1901.06943v1 [cond-mat.mtrl-sci])

2019-01-23T02:29:34+00:00January 23rd, 2019|Categories: Publications|Tags: |

Atomically thin films of III-VI post-transition metal chalcogenides (InSe and GaSe) form an interesting class of two-dimensional semiconductor that feature strong variations of their band gap as a function of the number of layers in the crystal [1-4] and, specifically for InSe, an earlier predicted crossover from a direct gap in the bulk [5,6] to a weakly indirect band gap in monolayers and bilayers [7-11]. Here, we apply angle resolved photoemission spectroscopy with submicrometer spatial resolution ($mu$ARPES) to visualise the layer-dependent valence band structure of mechanically exfoliated crystals of InSe. We show that for 1 layer and 2 layer InSe the valence band maxima are away from the $mathbf{Gamma}$-point, forming an indirect gap, with the conduction band edge known to be at the $mathbf{Gamma}$-point. In contrast, for six or more layers the bandgap becomes direct, in good agreement with theoretical predictions. The high-quality monolayer and bilayer samples enables us to resolve, in the photoluminescence spectra, the band-edge exciton (A) from the exciton (B) involving holes in a pair of deeper valence bands, degenerate at $mathbf{Gamma}$, with the splitting that agrees with both $mu$ARPES data and the results of DFT modelling. Due to the difference in symmetry between these two valence bands, light emitted by the A-exciton should be predominantly polarised perpendicular to the plane of the two-dimensional crystal, which we have verified for few-layer InSe crystals.

Published in: "arXiv Material Science".

Photoquantum Hall Effect and Light‐Induced Charge Transfer at the Interface of Graphene/InSe Heterostructures

2019-01-21T22:33:08+00:00January 21st, 2019|Categories: Publications|Tags: , , |

InSe‐capped graphene field effect transistors combine the photosensitivity of InSe with the unique electrical properties of graphene. The light‐induced charge transfer at the InSe/graphene interface can induce an increase or decrease of the carrier density in graphene and a light‐induced transition from a hole‐ to an electron‐carrier current, with potential for quantum metrology and miniaturized optical sensors and switches. Abstract The transfer of electronic charge across the interface of two van der Waals crystals can underpin the operation of a new class of functional devices. Among van der Waals semiconductors, an exciting and rapidly growing development involves the “post‐transition” metal chalcogenide InSe. Here, field effect phototransistors are reported where single layer graphene is capped with n‐type InSe. These device structures combine the photosensitivity of InSe with the unique electrical properties of graphene. It is shown that the light‐induced transfer of charge between InSe and graphene offers an effective method to increase or decrease the carrier density in graphene, causing a change in its resistance that is gate‐controllable and only weakly dependent on temperature. The charge transfer at the InSe/graphene interface is probed by Hall effect and photoconductivity measurmentes and it is demonstrated that light can induce a sign reversal of the quantum Hall voltage and photovoltaic effects in the graphene layer. These findings demonstrate the potential of light‐induced charge transfer in gate‐tunable InSe/graphene phototransistors for optoelectronics and quantum metrology.

Published in: "Advanced Functional Materials".

Experimental identification of critical condition for drastically enhancing thermoelectric power factor of two-dimensional layered materials. (arXiv:1811.11592v1 [cond-mat.mes-hall])

2018-11-29T04:30:19+00:00November 29th, 2018|Categories: Publications|Tags: , |

Nano-structuring is an extremely promising path to high performance thermoelectrics. Favorable improvements in thermal conductivity are attainable in many material systems, and theoretical work points to large improvements in electronic properties. However, realization of the electronic benefits in practical materials has been elusive experimentally. A key challenge is that experimental identification of the quantum confinement length, below which the thermoelectric power factor is significantly enhanced, remains elusive due to lack of simultaneous control of size and carrier density. Here we investigate gate tunable and temperature-dependent thermoelectric transport in $gamma$ phase indium selenide ($gamma$ InSe, n type semiconductor) samples with thickness varying from 7 to 29 nm. This allows us to properly map out dimension and doping space. Combining theoretical and experimental studies, we reveal that the sharper pre-edge of the conduction-band density of states arising from quantum confinement gives rise to an enhancement of the Seebeck coefficient and the power factor in the thinner InSe samples. Most importantly, we experimentally identify the role of the competition between quantum confinement length and thermal de Broglie wavelength in the enhancement of power factor. Our results provide an important and general experimental guideline for optimizing the power factor and improving the thermoelectric performance of two-dimensional layered semiconductors.

Published : "arXiv Mesoscale and Nanoscale Physics".

Photoquantum Hall Effect and Light‐Induced Charge Transfer at the Interface of Graphene/InSe Heterostructures

2018-11-28T22:32:38+00:00November 28th, 2018|Categories: Publications|Tags: , , |

InSe‐capped graphene field effect transistors combine the photosensitivity of InSe with the unique electrical properties of graphene. The light‐induced charge transfer at the InSe/graphene interface can induce an increase or decrease of the carrier density in graphene and a light‐induced transition from a hole‐ to an electron‐carrier current, with potential for quantum metrology and miniaturized optical sensors and switches. Abstract The transfer of electronic charge across the interface of two van der Waals crystals can underpin the operation of a new class of functional devices. Among van der Waals semiconductors, an exciting and rapidly growing development involves the “post‐transition” metal chalcogenide InSe. Here, field effect phototransistors are reported where single layer graphene is capped with n‐type InSe. These device structures combine the photosensitivity of InSe with the unique electrical properties of graphene. It is shown that the light‐induced transfer of charge between InSe and graphene offers an effective method to increase or decrease the carrier density in graphene, causing a change in its resistance that is gate‐controllable and only weakly dependent on temperature. The charge transfer at the InSe/graphene interface is probed by Hall effect and photoconductivity measurmentes and it is demonstrated that light can induce a sign reversal of the quantum Hall voltage and photovoltaic effects in the graphene layer. These findings demonstrate the potential of light‐induced charge transfer in gate‐tunable InSe/graphene phototransistors for optoelectronics and quantum metrology.

Published in: "Advanced Functional Materials".

Photoquantum Hall Effect and Light‐Induced Charge Transfer at the Interface of Graphene/InSe Heterostructures

2018-11-27T14:32:32+00:00November 27th, 2018|Categories: Publications|Tags: , , |

InSe‐capped graphene field effect transistors combine the photosensitivity of InSe with the unique electrical properties of graphene. The light‐induced charge transfer at the InSe/graphene interface can induce an increase or decrease of the carrier density in graphene and a light‐induced transition from a hole‐ to an electron‐carrier current, with potential for quantum metrology and miniaturized optical sensors and switches. Abstract The transfer of electronic charge across the interface of two van der Waals crystals can underpin the operation of a new class of functional devices. Among van der Waals semiconductors, an exciting and rapidly growing development involves the “post‐transition” metal chalcogenide InSe. Here, field effect phototransistors are reported where single layer graphene is capped with n‐type InSe. These device structures combine the photosensitivity of InSe with the unique electrical properties of graphene. It is shown that the light‐induced transfer of charge between InSe and graphene offers an effective method to increase or decrease the carrier density in graphene, causing a change in its resistance that is gate‐controllable and only weakly dependent on temperature. The charge transfer at the InSe/graphene interface is probed by Hall effect and photoconductivity measurmentes and it is demonstrated that light can induce a sign reversal of the quantum Hall voltage and photovoltaic effects in the graphene layer. These findings demonstrate the potential of light‐induced charge transfer in gate‐tunable InSe/graphene phototransistors for optoelectronics and quantum metrology.

Published in: "Advanced Functional Materials".

Electronic and optical properties of SnX2(X=S, Se)-InSe van der Waals heterostructures from first- principle calculations. (arXiv:1811.09031v1 [cond-mat.mtrl-sci])

2018-11-26T02:29:28+00:00November 26th, 2018|Categories: Publications|Tags: , |

In this work from first-principles simulations we investigate bilayer van der Waals heterostructures (vdWh) of emerging 2-dimensional (2D) optical materials SnS 2 and SnSe 2 with monolayer InSe. With density functional theory (DFT) calculations, we study the structural, electronic, optical and carrier transport properties of the SnX 2 (X=S,Se)-InSe vdWh. Calculations show SnX 2 -InSe in its most stable stacking form (named AB-1) to be a material with a small (0.6- 0.7eV) indirect band-gap. The bilayer vdWh shows broad spectrum optical response, with number of peaks in the infra-red to visible region. In terms of carrier transport properties, asymmetry in conductance was observed with respect to the transport direction and electron and hole transmission. The findings are promising from the viewpoint of nanoelectronics and photonics.

Published in: "arXiv Material Science".

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