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Title: High-performance multilayer WSe 2 field-effect transistors with carrier type control

Abstract

In this paper, high-performance multilayer WSe 2 field-effect transistor (FET) devices with carrier type control are demonstrated via thickness modulation and a remote oxygen plasma surface treatment. Carrier type control in multilayer WSe 2 FET devices with Cr/Au contacts is initially demonstrated by modulating the WSe 2 thickness. The carrier type evolves with increasing WSe 2 channel thickness, being p-type, ambipolar, and n-type at thicknesses <3, ~4, and >5 nm, respectively. The thickness-dependent carrier type is attributed to changes in the bandgap of WSe 2 as a function of the thickness and the carrier band offsets relative to the metal contacts. Furthermore, we present a strong hole carrier doping effect via remote oxygen plasma treatment. It non-degenerately converts n-type characteristics into p-type and enhances field-effect hole mobility by three orders of magnitude. Finally, this work demonstrates progress towards the realization of high-performance multilayer WSe 2 FETs with carrier type control, potentially extendable to other transition metal dichalcogenides, for future electronic and optoelectronic applications.

Authors:
 [1];  [2];  [1];  [3];  [3];  [3];  [3];  [4];  [5];  [5];  [6];  [1]
  1. Univ. of Tennessee, Knoxville, TN (United States). Dept. of Materials Science and Engineering; Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Sciences
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Sciences; Univ. of Tennessee, Knoxville, TN (United States). Bredesen Center for Interdisciplinary Research and Graduate Education
  3. Univ. of Tennessee, Knoxville, TN (United States). Dept. of Materials Science and Engineering
  4. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Sciences
  5. Univ. of Tennessee, Knoxville, TN (United States). Dept. of Materials Science and Engineering; Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science and Technology Division
  6. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science and Technology Division
Publication Date:
Research Org.:
Univ. of Tennessee, Knoxville, TN (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); USDOE Laboratory Directed Research and Development (LDRD) Program; Gordon and Betty Moore Foundation (United States); National Science Foundation (NSF)
OSTI Identifier:
1376482
Alternate Identifier(s):
OSTI ID: 1423050
Grant/Contract Number:
AC05-00OR22725; SC0002136; GBMF4416; DMR-1410940
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Nano Research
Additional Journal Information:
Journal Volume: 11; Journal Issue: 2; Journal ID: ISSN 1998-0124
Publisher:
Springer
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; transition metal dichalcogenide; field-effect transistors; carrier control; plasma treatment; carrier mobility

Citation Formats

Pudasaini, Pushpa Raj, Oyedele, Akinola, Zhang, Cheng, Stanford, Michael G., Cross, Nicholas, Wong, Anthony T., Hoffman, Anna N., Xiao, Kai, Duscher, Gerd, Mandrus, David G., Ward, Thomas Z., and Rack, Philip D. High-performance multilayer WSe2 field-effect transistors with carrier type control. United States: N. p., 2017. Web. doi:10.1007/s12274-017-1681-5.
Pudasaini, Pushpa Raj, Oyedele, Akinola, Zhang, Cheng, Stanford, Michael G., Cross, Nicholas, Wong, Anthony T., Hoffman, Anna N., Xiao, Kai, Duscher, Gerd, Mandrus, David G., Ward, Thomas Z., & Rack, Philip D. High-performance multilayer WSe2 field-effect transistors with carrier type control. United States. doi:10.1007/s12274-017-1681-5.
Pudasaini, Pushpa Raj, Oyedele, Akinola, Zhang, Cheng, Stanford, Michael G., Cross, Nicholas, Wong, Anthony T., Hoffman, Anna N., Xiao, Kai, Duscher, Gerd, Mandrus, David G., Ward, Thomas Z., and Rack, Philip D. Thu . "High-performance multilayer WSe2 field-effect transistors with carrier type control". United States. doi:10.1007/s12274-017-1681-5.
@article{osti_1376482,
title = {High-performance multilayer WSe2 field-effect transistors with carrier type control},
author = {Pudasaini, Pushpa Raj and Oyedele, Akinola and Zhang, Cheng and Stanford, Michael G. and Cross, Nicholas and Wong, Anthony T. and Hoffman, Anna N. and Xiao, Kai and Duscher, Gerd and Mandrus, David G. and Ward, Thomas Z. and Rack, Philip D.},
abstractNote = {In this paper, high-performance multilayer WSe2 field-effect transistor (FET) devices with carrier type control are demonstrated via thickness modulation and a remote oxygen plasma surface treatment. Carrier type control in multilayer WSe2 FET devices with Cr/Au contacts is initially demonstrated by modulating the WSe2 thickness. The carrier type evolves with increasing WSe2 channel thickness, being p-type, ambipolar, and n-type at thicknesses <3, ~4, and >5 nm, respectively. The thickness-dependent carrier type is attributed to changes in the bandgap of WSe2 as a function of the thickness and the carrier band offsets relative to the metal contacts. Furthermore, we present a strong hole carrier doping effect via remote oxygen plasma treatment. It non-degenerately converts n-type characteristics into p-type and enhances field-effect hole mobility by three orders of magnitude. Finally, this work demonstrates progress towards the realization of high-performance multilayer WSe2 FETs with carrier type control, potentially extendable to other transition metal dichalcogenides, for future electronic and optoelectronic applications.},
doi = {10.1007/s12274-017-1681-5},
journal = {Nano Research},
number = 2,
volume = 11,
place = {United States},
year = {Thu Jul 06 00:00:00 EDT 2017},
month = {Thu Jul 06 00:00:00 EDT 2017}
}

Journal Article:
Free Publicly Available Full Text
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  • In this study, high-performance multilayer WSe2 field-effect transistor (FET) devices with carrier type control are demonstrated via thickness modulation and a remote oxygen plasma surface treatment. Carrier type control in multilayer WSe2 FET devices with Cr/Au contacts is initially demonstrated by modulating the WSe2 thickness. The carrier type evolves with increasing WSe2 channel thickness, being p-type, ambipolar, and n-type at thicknesses <3, ~4, and >5 nm, respectively. The thickness-dependent carrier type is attributed to changes in the bandgap of WSe2 as a function of the thickness and the carrier band offsets relative to the metal contacts. Furthermore, we present amore » strong hole carrier doping effect via remote oxygen plasma treatment. It non-degenerately converts n-type characteristics into p-type and enhances field-effect hole mobility by three orders of magnitude. This work demonstrates progress towards the realization of high-performance multilayer WSe2 FETs with carrier type control, potentially extendable to other transition metal dichalcogenides, for future electronic and optoelectronic applications.« less
    Cited by 1
  • Two-dimensional materials have outstanding scalability due to their structural and electrical properties for the logic devices. Here, we report the current fluctuation in multilayer WSe{sub 2} field effect transistors (FETs). In order to demonstrate the impact on carrier types, n-type and p-type WSe{sub 2} FETs are fabricated with different work function metals. Each device has similar electrical characteristics except for the threshold voltage. In the low frequency noise analysis, drain current power spectral density (S{sub I}) is inversely proportional to frequency, indicating typical 1/f noise behaviors. The curves of the normalized drain current power spectral density (NS{sub I}) as amore » function of drain current at the 10 Hz of frequency indicate that our devices follow the carrier number fluctuation with correlated mobility fluctuation model. This means that current fluctuation depends on the trapping-detrapping motion of the charge carriers near the channel interface. No significant difference is observed in the current fluctuation according to the charge carrier type, electrons and holes that occurred in the junction and channel region.« less
  • In this article, first, we show that by contact work function engineering, electrostatic doping and proper scaling of both the oxide thickness and the flake thickness, high performance p- and n-type WSe{sub 2} field effect transistors (FETs) can be realized. We report record high drive current of 98 μA/μm for the electron conduction and 110 μA/μm for the hole conduction in Schottky barrier WSe{sub 2} FETs. Then, we combine high performance WSe{sub 2} PFET with WSe{sub 2} NFET in double gated transistor geometry to demonstrate a fully complementary logic inverter. We also show that by adjusting the threshold voltages for themore » NFET and the PFET, the gain and the noise margin of the inverter can be significantly enhanced. The maximum gain of our chemical doping free WSe{sub 2} inverter was found to be ∼25 and the noise margin was close to its ideal value of ∼2.5 V for a supply voltage of V{sub DD} = 5.0 V.« less
  • Here, we report a new strategy for fabricating 2D/2D low-resistance ohmic contacts for a variety of transition metal dichalcogenides (TMDs) using van der Waals assembly of substitutionally doped TMDs as drain/source contacts and TMDs with no intentional doping as channel materials. We demonstrate that few-layer WSe 2 field-effect transistors (FETs) with 2D/2D contacts exhibit low contact resistances of ~0.3 kΩ μm, high on/off ratios up to >10 9, and high drive currents exceeding 320 μA μm –1. These favorable characteristics are combined with a two-terminal field-effect hole mobility μ FE ≈ 2 × 10 2 cm 2 V –1 smore » –1 at room temperature, which increases to >2 × 10 3 cm 2 V –1 s –1 at cryogenic temperatures. We observe a similar performance also in MoS 2 and MoSe 2 FETs with 2D/2D drain and source contacts. The 2D/2D low-resistance ohmic contacts presented here represent a new device paradigm that overcomes a significant bottleneck in the performance of TMDs and a wide variety of other 2D materials as the channel materials in postsilicon electronics.« less
  • Two key subjects stand out in the pursuit of semiconductor research: material quality and contact technology. The fledging field of atomically thin transition metal dichalcogenides (TMDCs) faces a number of challenges in both efforts. This work attempts to establish a connection between the two by examining the gate-dependent conductance of few-layer (1-5L) WSe{sub 2} field effect devices. Measurements and modeling of the subgap regime reveal Schottky barrier transistor behavior. We show that transmission through the contact barrier is dominated by thermionic field emission (TFE) at room temperature, despite the lack of intentional doping. The TFE process arises due to amore » large number of subgap impurity states, the presence of which also leads to high mobility edge carrier densities. The density of states of such impurity states is self-consistently determined to be approximately 1–2 × 10{sup 13}/cm{sup 2}/eV in our devices. We demonstrate that substrate is unlikely to be a major source of the impurity states and suspect that lattice defects within the material itself are primarily responsible. Our experiments provide key information to advance the quality and understanding of TMDC materials and electrical devices.« less