Name: electric-field control of electronic states in ws2 nanodevices by electrolyte gating
Uploaded: 2018-04-12T13:30:00
Description: Watch this Scientific Journal Video about Electric-field Control of Electronic States in WS2 Nanodevices by Electrolyte Gating at JoVE.com

We acknowledge the following financial support; Grant-in-Aid for Specially Promoted Research (No. 25000003) from JSPS, Grant-in-Aid for Research Activity Start-up (No.15H06133) and Challenging Research (Exploratory) (No. JP17K18748) from MEXT of Japan.

1. Dispersion of WS 2 Nanotubes (NTs) on substrate
<ol>
	<li>Disperse WS2 NT powders into isopropyl alcohol (IPA, concentration more than 99.8%) with proper diluted ratio (about 0.1 mg/mL) by sonication for 20 min. 
	NOTE: The long-time sonication helps to make WS2 NTs uniformly suspended in IPA liquid and to separate well-formed individual WS2 NTs from amorphous WS2 or other junks, as well as to remove the garbage accumulating on WS2 NTs surface. <...

In both WS2 NTs and flakes, we have successfully controlled the electric properties by electrostatic or electro chemical carrier doping.
In electrostatic doping region, ambipolar transistor operation has been observed. Such ambipolar transfer curve with a high on/off ratio (&#62;102) observed in low bias voltage indicates the effective carrier doping at the interface of electrolyte gating technique for tuning the Fermi level of these systems.
A...

Control of the carrier number is the key technique for realizing the quantum phase transition in solids1. In the conventional field effect transistor (FET), it is achieved by use of the solid gate1,2. In such a device, electric potential gradient is uniform throughout the dielectric materials so that induced carrier number at the interface is limited, shown in Figure 1a.
On the other hand, we can achieve the higher carrier density at the interface or bulk by replacing the solid dielectric materials with ionic gels/liquids or polymer electrolytes3,4,5,6,7,8,9,10,11 (Figure 1b). In the electrostatic doping by use of the ionic liquid, electric double layer transistor (EDLT) structure is formed at the interface between ionic liquid and sample, generating strong electric field (&#62;0.5 V/&#197;) even at low bias voltage. Resultant high carrier density (&#62;1014 cm-2) induced at the interface10,12,13 cause the novel electronic properties or quantum phase transition such as electric-field-induced ferromagnetism14, Coulomb blockade15, ambipolar transport16,17,18,19,20,21,22,23,24,25,26,27, formation of p-n junction and resultant electroluminance28,29,30, large modulation of thermoelectric powers31,32, charge density wave and Mott transitions33,34,35, and electric-field-induced insulator-metal transition36,37 including electric-field-induced superconductivity9,10,11,38,39,40,41,42,43,44,45,46,47,48,49.
In the electrolyte gating (Figure 1c), ions are not only accumulated at the interface to form EDLT, but can be also intercalated into layers of two-dimensional materials via thermal diffusion without damaging sample under applying the large gate voltage, leading to the electrochemical doping8,9,11,34,38,50,51,52,53. Thus, we can drastically change the carrier number compared to the conventional field effect transistor using the solid gate. In particular, the electric-field-induced superconductivity9,11,34,38,50 is realized by use of electrolyte gating in region of large carrier number where we cannot access by the conventional solid gating method.
In this article, we introduce this unique technique of carrier number control in solids and overview the transistor operation and electric-field-induced superconductivity in semiconducting WS2 samples such as WS2 flakes and WS2 nanotubes54,55,56,57.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Sonication machine</td>
			<td>SND Co., Ltd.</td>
			<td>US-2</td>
			<td>http://www.senjyou.jp/</td>
		</tr>
		<tr>
			<td>Spin-coater machine</td>
			<td>ACTIVE Co.,Ltd.</td>
			<td>ACT-300AII</td>
			<td>http://www.acti-ve.co.jp/spincoater/standard/act300a2.html</td>
		</tr>
		<tr>
			<td>Hot-plate</td>
			<td>TAIYO</td>
			<td>HP131224</td>
			<td>http://www.taiyo-kabu.co.jp/products/detail.php?product_id=431</td>
		</tr>
		<tr>
			<td>Optical Microscopy</td>
			<td>OLYMPUS</td>
			<td>BX51</td>
			<td>https://www.olympus-ims.com/ja/microscope/bx51p/</td>
		</tr>
		<tr>
			<td>Electron Beam Lithography machine</td>
			<td>ELIONIX INC.</td>
			<td>ELS-7500I</td>
			<td>https://www.elionix.co.jp/index.html</td>
		</tr>
		<tr>
			<td>Scribing machine</td>
			<td>TOKYO SEIMITSU CO., LTD.</td>
			<td>A-WS-100A</td>
			<td>http://www.accretech.jp/english/product/semicon/wms/aws100s.html</td>
		</tr>
		<tr>
			<td>Wire-bonding machine</td>
			<td>WEST&#183;BOND&#160;</td>
			<td>7476D-79</td>
			<td>https://www.hisol.jp/products/bonder/wire/mgb/b.html</td>
		</tr>
		<tr>
			<td>Physical Properties Measurement System</td>
			<td>Quantum Design</td>
			<td>PPMS</td>
			<td>http://www.qdusa.com/products/ppms.html</td>
		</tr>
		<tr>
			<td>Lock-in amplifier</td>
			<td>Stanford Research Systems</td>
			<td>SRS830</td>
			<td>http://www.thinksrs.com/products/SR810830.htm</td>
		</tr>
		<tr>
			<td>Source meter</td>
			<td>Textronix</td>
			<td>KEITHLEY 2612A</td>
			<td>http://www.tek.com/keithley-source-measure-units/smu-2600b-series-sourcemeter</td>
		</tr>
		<tr>
			<td>KClO4</td>
			<td>Sigma-Aldrich</td>
			<td>241830</td>
			<td>http://www.sigmaaldrich.com/catalog/product/sigald/241830?lang=ja&#38;region=JP</td>
		</tr>
		<tr>
			<td>PEG</td>
			<td>WAKO</td>
			<td>168-09075</td>
			<td>http://www.siyaku.com/uh/Shs.do?dspCode=W01W0116-0907</td>
		</tr>
		<tr>
			<td>IPA</td>
			<td>WAKO</td>
			<td>169-28121</td>
			<td>http://www.siyaku.com/uh/Shs.do?dspWkfcode=169-28121</td>
		</tr>
		<tr>
			<td>MIBK</td>
			<td>WAKO</td>
			<td>131-05645</td>
			<td>http://www.siyaku.com/uh/Shs.do?dspCode=W01W0113-0564</td>
		</tr>
		<tr>
			<td>PMMA</td>
			<td>MicroChem</td>
			<td>PMMA</td>
			<td>http://microchem.com/Prod-PMMA.htm</td>
		</tr>
		<tr>
			<td>Acetone</td>
			<td>WAKO</td>
			<td>012-26821</td>
			<td>http://www.siyaku.com/uh/Shs.do?dspWkfcode=012-26821</td>
		</tr>
	</tbody>
</table>

electric-field control of electronic states in ws2 nanodevices by electrolyte gating

A method of carrier number control by electrolyte gating is demonstrated. We have obtained WS2 thin flakes with atomically flat surface via scotch tape method or individual WS2 nanotubes by dispersing the suspension of WS2 nanotubes. The selected samples have been fabricated into devices by the use of the electron beam lithography and electrolyte is put on the devices. We have characterized the electronic properties of the devices under applying the gate voltage. In the small gate voltage region, ions in the electrolyte are accumulated on the surface of the samples which leads to the large electric potential drop and resultant electrostatic carrier doping at the interface. Ambipolar transfer curve has been observed in this electrostatic doping region. When the gate voltage is further increased, we met another drastic increase of source-drain current which implies that ions are intercalated into layers of WS2 and electrochemical carrier doping is realized. In such electrochemical doping region, superconductivity has been observed. The focused technique provides a powerful strategy for achieving the electric-filed-induced quantum phase transition.

The typical transistor operations of an individual WS2 NT and a WS2 flake devices are shown in Figure 3a and 3b, respectively, where the source drain current (IDS) as a function of the gate voltage (VG) nicely operates in an ambipolar mode, showing a remarkable contrast to the unipolar gate response by the conventional solid gated FET in previous publication58</su...

Watch this Scientific Journal Video about Electric-field Control of Electronic States in WS2 Nanodevices by Electrolyte Gating at JoVE.com

Electric-field Control of Electronic States in WS2 Nanodevices by Electrolyte Gating

Here, we present a protocol to control the carrier number in solids by using the electrolyte.

Electric-field Control of Electronic States in WS2 Nanodevices by Electrolyte Gating

A method of carrier number control by electrolyte gating is demonstrated. We have obtained WS2 thin flakes with atomically flat surface via scotch tape ...

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