In2Se3

/Tag: In2Se3

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".

Nonvolatile Ferroelectric Memory Effect in Ultrathin α‐In2Se3

2019-03-10T20:32:30+00:00March 10th, 2019|Categories: Publications|Tags: , |

A prototype of a 2D ferroelectric memory device is demonstrated. The nonvolatile functionality stems from the room‐temperature out‐of‐plane ferroelectricity in ultrathin α‐In2Se3. The hybrid ferroelectric field‐effect transistor allows not only the control and probe of electric dipoles, but also the quantitative measurement of the electric polarization in atomically thin van der Waals ferroelectrics. Abstract High‐density memory is integral in solid‐state electronics. 2D ferroelectrics offer a new platform for developing ultrathin electronic devices with nonvolatile functionality. Recent experiments on layered α‐In2Se3 confirm its room‐temperature out‐of‐plane ferroelectricity under ambient conditions. Here, a nonvolatile memory effect in a hybrid 2D ferroelectric field‐effect transistor (FeFET) made of ultrathin α‐In2Se3 and graphene is demonstrated. The resistance of the graphene channel in the FeFET is effectively controllable and retentive due to the electrostatic doping, which stems from the electric polarization of the ferroelectric α‐In2Se3. The electronic logic bit can be represented and stored with different orientations of electric dipoles in the top‐gate ferroelectric. The 2D FeFET can be randomly rewritten over more than 105 cycles without losing the nonvolatility. The approach demonstrates a prototype of rewritable nonvolatile memory with ferroelectricity in van der Waals 2D materials.

Published in: "Advanced Functional Materials".

Nonvolatile Ferroelectric Memory Effect in Ultrathin α‐In2Se3

2019-02-28T06:32:36+00:00February 28th, 2019|Categories: Publications|Tags: , |

A prototype of a 2D ferroelectric memory device is demonstrated. The nonvolatile functionality stems from the room‐temperature out‐of‐plane ferroelectricity in ultrathin α‐In2Se3. The hybrid ferroelectric field‐effect transistor allows not only the control and probe of electric dipoles, but also the quantitative measurement of the electric polarization in atomically thin van der Waals ferroelectrics. Abstract High‐density memory is integral in solid‐state electronics. 2D ferroelectrics offer a new platform for developing ultrathin electronic devices with nonvolatile functionality. Recent experiments on layered α‐In2Se3 confirm its room‐temperature out‐of‐plane ferroelectricity under ambient conditions. Here, a nonvolatile memory effect in a hybrid 2D ferroelectric field‐effect transistor (FeFET) made of ultrathin α‐In2Se3 and graphene is demonstrated. The resistance of the graphene channel in the FeFET is effectively controllable and retentive due to the electrostatic doping, which stems from the electric polarization of the ferroelectric α‐In2Se3. The electronic logic bit can be represented and stored with different orientations of electric dipoles in the top‐gate ferroelectric. The 2D FeFET can be randomly rewritten over more than 105 cycles without losing the nonvolatility. The approach demonstrates a prototype of rewritable nonvolatile memory with ferroelectricity in van der Waals 2D materials.

Published in: "Advanced Functional Materials".

Nonvolatile Ferroelectric Memory Effect in Ultrathin α‐In2Se3

2019-02-26T12:32:51+00:00February 26th, 2019|Categories: Publications|Tags: , |

A prototype of a 2D ferroelectric memory device is demonstrated. The nonvolatile functionality stems from the room‐temperature out‐of‐plane ferroelectricity in ultrathin α‐In2Se3. The hybrid ferroelectric field‐effect transistor allows not only the control and probe of electric dipoles, but also the quantitative measurement of the electric polarization in atomically thin van der Waals ferroelectrics. Abstract High‐density memory is integral in solid‐state electronics. 2D ferroelectrics offer a new platform for developing ultrathin electronic devices with nonvolatile functionality. Recent experiments on layered α‐In2Se3 confirm its room‐temperature out‐of‐plane ferroelectricity under ambient conditions. Here, a nonvolatile memory effect in a hybrid 2D ferroelectric field‐effect transistor (FeFET) made of ultrathin α‐In2Se3 and graphene is demonstrated. The resistance of the graphene channel in the FeFET is effectively controllable and retentive due to the electrostatic doping, which stems from the electric polarization of the ferroelectric α‐In2Se3. The electronic logic bit can be represented and stored with different orientations of electric dipoles in the top‐gate ferroelectric. The 2D FeFET can be randomly rewritten over more than 105 cycles without losing the nonvolatility. The approach demonstrates a prototype of rewritable nonvolatile memory with ferroelectricity in van der Waals 2D materials.

Published in: "Advanced Functional Materials".

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".

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".

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".

Room‐Temperature Ferroelectricity in Hexagonally Layered α‐In2Se3 Nanoflakes down to the Monolayer Limit

2018-11-11T04:32:19+00:00November 11th, 2018|Categories: Publications|Tags: , |

The thinnest layered ferroelectric is demonstrated for the first time at room temperature. The semiconducting hexagonal α‐In2Se3 nanoflakes exhibit out‐of‐plane and in‐plane ferroelectricity that are closely intercorrelated. The polarization switching and hysteresis loops can be realized in the thickness as thin as ≈2.3 nm (bilayer) and ≈1.2 nm (monolayer). Two types of ferroelectric switchable devices are proposed to show the potential application in nonvolatile memories. Abstract 2D ferroelectric material has emerged as an attractive building block for high‐density data storage nanodevices. Although monolayer van der Waals ferroelectrics have been theoretically predicted, a key experimental breakthrough for such calculations is still not realized. Here, hexagonally stacking α‐In2Se3 nanoflake, a rarely studied van der Waals polymorph, is reported to exhibit out‐of‐plane (OOP) and in‐plane (IP) ferroelectricity at room temperature. Ferroelectric multidomain states in a hexagonal α‐In2Se3 nanoflake with uniform thickness can survive to 6 nm. Most strikingly, the electric‐field‐induced polarization switching and hysteresis loop are, respectively, observed down to the bilayer and monolayer (≈1.2 nm) thicknesses, which designates it as the thinnest layered ferroelectric and verifies the corresponding theoretical calculation. In addition, two types of ferroelectric nanodevices employing the OOP and IP polarizations in 2H α‐In2Se3 are developed, which are applicable for nonvolatile memories and heterostructure‐based nanoelectronics/optoelectronics.

Published in: "Advanced Functional Materials".

High Mobilities in Layered InSe Transistors with Indium‐Encapsulation‐Induced Surface Charge Doping

2018-11-10T22:34:25+00:00November 10th, 2018|Categories: Publications|Tags: , |

A robust layered indium selenide (InSe) field‐effect transistor (FET) with superior high mobility (3700 cm2 V−1 s−1 at room temperature) is demonstrated by depositing an indium doping layer. With tunable carrier transport, the surface‐doped InSe FETs present flexible operations to realize various logic circuits, such as inverters and not‐or and not‐and gates. Abstract Tunability and stability in the electrical properties of 2D semiconductors pave the way for their practical applications in logic devices. A robust layered indium selenide (InSe) field‐effect transistor (FET) with superior controlled stability is demonstrated by depositing an indium (In) doping layer. The optimized InSe FETs deliver an unprecedented high electron mobility up to 3700 cm2 V−1 s−1 at room temperature, which can be retained with 60% after 1 month. Further insight into the evolution of the position of the Fermi level and the microscopic device structure with different In thicknesses demonstrates an enhanced electron‐doping behavior at the In/InSe interface. Furthermore, the contact resistance is also improved through the In insertion between InSe and Au electrodes, which coincides with the analysis of the low‐frequency noise. The carrier fluctuation is attributed to the dominance of the phonon scattering events, which agrees with the observation of the temperature‐dependent mobility. Finally, the flexible functionalities of the logic‐circuit applications, for instance, inverter and not‐and (NAND)/not‐or (NOR) gates, are determined with these surface‐doping InSe FETs, which establish a paradigm for 2D‐based materials to overcome the bottleneck in the development of electronic devices.

Published in: "Advanced Materials".

High Mobilities in Layered InSe Transistors with Indium‐Encapsulation‐Induced Surface Charge Doping

2018-11-07T10:34:02+00:00November 7th, 2018|Categories: Publications|Tags: , |

A robust layered indium selenide (InSe) field‐effect transistor (FET) with superior high mobility (3700 cm2 V−1 s−1 at room temperature) is demonstrated by depositing an indium doping layer. With tunable carrier transport, the surface‐doped InSe FETs present flexible operations to realize various logic circuits, such as inverters and not‐or and not‐and gates. Abstract Tunability and stability in the electrical properties of 2D semiconductors pave the way for their practical applications in logic devices. A robust layered indium selenide (InSe) field‐effect transistor (FET) with superior controlled stability is demonstrated by depositing an indium (In) doping layer. The optimized InSe FETs deliver an unprecedented high electron mobility up to 3700 cm2 V−1 s−1 at room temperature, which can be retained with 60% after 1 month. Further insight into the evolution of the position of the Fermi level and the microscopic device structure with different In thicknesses demonstrates an enhanced electron‐doping behavior at the In/InSe interface. Furthermore, the contact resistance is also improved through the In insertion between InSe and Au electrodes, which coincides with the analysis of the low‐frequency noise. The carrier fluctuation is attributed to the dominance of the phonon scattering events, which agrees with the observation of the temperature‐dependent mobility. Finally, the flexible functionalities of the logic‐circuit applications, for instance, inverter and not‐and (NAND)/not‐or (NOR) gates, are determined with these surface‐doping InSe FETs, which establish a paradigm for 2D‐based materials to overcome the bottleneck in the development of electronic devices.

Published in: "Advanced Materials".

High Mobilities in Layered InSe Transistors with Indium‐Encapsulation‐Induced Surface Charge Doping

2018-11-07T00:35:18+00:00November 6th, 2018|Categories: Publications|Tags: , |

A robust layered indium selenide (InSe) field‐effect transistor (FET) with superior high mobility (3700 cm2 V−1 s−1 at room temperature) is demonstrated by depositing an indium doping layer. With tunable carrier transport, the surface‐doped InSe FETs present flexible operations to realize various logic circuits, such as inverters and not‐or and not‐and gates. Abstract Tunability and stability in the electrical properties of 2D semiconductors pave the way for their practical applications in logic devices. A robust layered indium selenide (InSe) field‐effect transistor (FET) with superior controlled stability is demonstrated by depositing an indium (In) doping layer. The optimized InSe FETs deliver an unprecedented high electron mobility up to 3700 cm2 V−1 s−1 at room temperature, which can be retained with 60% after 1 month. Further insight into the evolution of the position of the Fermi level and the microscopic device structure with different In thicknesses demonstrates an enhanced electron‐doping behavior at the In/InSe interface. Furthermore, the contact resistance is also improved through the In insertion between InSe and Au electrodes, which coincides with the analysis of the low‐frequency noise. The carrier fluctuation is attributed to the dominance of the phonon scattering events, which agrees with the observation of the temperature‐dependent mobility. Finally, the flexible functionalities of the logic‐circuit applications, for instance, inverter and not‐and (NAND)/not‐or (NOR) gates, are determined with these surface‐doping InSe FETs, which establish a paradigm for 2D‐based materials to overcome the bottleneck in the development of electronic devices.

Published in: "Advanced Materials".

Room‐Temperature Ferroelectricity in Hexagonally Layered α‐In2Se3 Nanoflakes down to the Monolayer Limit

2018-11-07T00:32:16+00:00November 6th, 2018|Categories: Publications|Tags: , |

The thinnest layered ferroelectric is demonstrated for the first time at room temperature. The semiconducting hexagonal α‐In2Se3 nanoflakes exhibit out‐of‐plane and in‐plane ferroelectricity that are closely intercorrelated. The polarization switching and hysteresis loops can be realized in the thickness as thin as ≈2.3 nm (bilayer) and ≈1.2 nm (monolayer). Two types of ferroelectric switchable devices are proposed to show the potential application in nonvolatile memories. Abstract 2D ferroelectric material has emerged as an attractive building block for high‐density data storage nanodevices. Although monolayer van der Waals ferroelectrics have been theoretically predicted, a key experimental breakthrough for such calculations is still not realized. Here, hexagonally stacking α‐In2Se3 nanoflake, a rarely studied van der Waals polymorph, is reported to exhibit out‐of‐plane (OOP) and in‐plane (IP) ferroelectricity at room temperature. Ferroelectric multidomain states in a hexagonal α‐In2Se3 nanoflake with uniform thickness can survive to 6 nm. Most strikingly, the electric‐field‐induced polarization switching and hysteresis loop are, respectively, observed down to the bilayer and monolayer (≈1.2 nm) thicknesses, which designates it as the thinnest layered ferroelectric and verifies the corresponding theoretical calculation. In addition, two types of ferroelectric nanodevices employing the OOP and IP polarizations in 2H α‐In2Se3 are developed, which are applicable for nonvolatile memories and heterostructure‐based nanoelectronics/optoelectronics.

Published in: "Advanced Functional Materials".

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