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Novel field-effect Schottky barrier transistors based on graphene-MoS2 heterojunctions.

Tian H, Tan Z, Wu C, Wang X, Mohammad MA, Xie D, Yang Y, Wang J, Li LJ, Xu J, Ren TL - Sci Rep (2014)

Bottom Line: Recently, two-dimensional materials such as molybdenum disulphide (MoS2) have been demonstrated to realize field effect transistors (FET) with a large current on-off ratio.Moreover, the field effective mobility of the FESBT is up to 58.7 cm(2)/V · s.Our theoretical analysis shows that if the thickness of oxide is further reduced, a subthreshold swing (SS) of 40 mV/decade can be maintained within three orders of drain current at room temperature.

View Article: PubMed Central - PubMed

Affiliation: 1] Institute of Microelectronics, Tsinghua University, Beijing 100084, China [2] Tsinghua National Laboratory for Information Science and Technology (TNList), Tsinghua University, Beijing 100084, China [3].

ABSTRACT
Recently, two-dimensional materials such as molybdenum disulphide (MoS2) have been demonstrated to realize field effect transistors (FET) with a large current on-off ratio. However, the carrier mobility in backgate MoS2 FET is rather low (typically 0.5-20 cm(2)/V · s). Here, we report a novel field-effect Schottky barrier transistors (FESBT) based on graphene-MoS2 heterojunction (GMH), where the characteristics of high mobility from graphene and high on-off ratio from MoS2 are properly balanced in the novel transistors. Large modulation on the device current (on/off ratio of 10(5)) is achieved by adjusting the backgate (through 300 nm SiO2) voltage to modulate the graphene-MoS2 Schottky barrier. Moreover, the field effective mobility of the FESBT is up to 58.7 cm(2)/V · s. Our theoretical analysis shows that if the thickness of oxide is further reduced, a subthreshold swing (SS) of 40 mV/decade can be maintained within three orders of drain current at room temperature. This provides an opportunity to overcome the limitation of 60 mV/decade for conventional CMOS devices. The FESBT implemented with a high on-off ratio, a relatively high mobility and a low subthreshold promises low-voltage and low-power applications for future electronics.

No MeSH data available.


Related in: MedlinePlus

The experimental results of the MoS2-Graphene-MoS2 FESBT (MGM-FESBT).(a) Schematic structure of the MGM-FESBT based on two graphene-MoS2 heterojunctions. (b) Optical image of the MGM heterojunction with few-layer MoS2 film and few-layer graphene film deposited onto a 300 nm SiO2/Si substrate. (c) AFM image of the MGM heterojunction. (d) The current vs. bias voltage characteristics of MGM-FESBT at various Vgate. The black arrow indicates the direction of increasing Vgate. (e) The current vs. gate voltage characteristics of MGM-FESBT at various Vbias. (f) The current vs. bias voltage characteristics demonstrating how current can be rectified by changing Vgate.
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f3: The experimental results of the MoS2-Graphene-MoS2 FESBT (MGM-FESBT).(a) Schematic structure of the MGM-FESBT based on two graphene-MoS2 heterojunctions. (b) Optical image of the MGM heterojunction with few-layer MoS2 film and few-layer graphene film deposited onto a 300 nm SiO2/Si substrate. (c) AFM image of the MGM heterojunction. (d) The current vs. bias voltage characteristics of MGM-FESBT at various Vgate. The black arrow indicates the direction of increasing Vgate. (e) The current vs. gate voltage characteristics of MGM-FESBT at various Vbias. (f) The current vs. bias voltage characteristics demonstrating how current can be rectified by changing Vgate.

Mentions: A novel MoS2-graphene-MoS2 FESBT (MGM-FESBT) is also demonstrated, which has an ability to rectify a current by changing the gate voltage. As shown in Figure 3a, the structure of the MGM-FESBT consists of two GMHs. Optical microscopy (Figure 3b) and AFM images (Figure 3c) show the structure of the MGM heterojunction. The thicknesses of the two MoS2 flakes are 40 nm and 24 nm, respectively. The graphene flake is 28 nm thick. The electrical characteristics of the two MoS2-graphene junctions show some differences (Supporting Figure S5) due the difference of thicknesses of MoS2 in two GMHs. The working principle of the MGM-FESBT can be described as follows. A large amount of electrons inject from the drain terminal to MoS2 and then drift into the graphene. Due to the schottky barrier between MoS2-graphene and the recombination with holes in graphene, only a fraction of the injected electrons can pass through the graphene and be collected by the MoS2 at the source terminal. As the work function of the graphene is tunable by the gate voltage, the Schottky barrier between MoS2-graphene could be tuned from the gate to improved contact. Figure 3d shows the current vs. bias voltage characteristics of MGM-FESBT at various Vgate. The black arrow indicates the direction of increasing Vgate. It indicates that the lower gate voltage can lead to a higher Schottky barrier height between MoS2 and graphene. Figure 3e shows the current vs. gate voltage characteristics of a MGM-FESBT at various Vbias. Figure 3f demonstrates that the barrier property of a MGM-FESBT is tunable by Vgate. At Vgate = −10 V, the Schottky contact is formed in the MGM. After the gate voltage is increased to 42 V, the contact barrier is lowered. This means that the MGM can realize a “diode” to “resistor” transition easily, which may open a wide application space in next generation electronics.


Novel field-effect Schottky barrier transistors based on graphene-MoS2 heterojunctions.

Tian H, Tan Z, Wu C, Wang X, Mohammad MA, Xie D, Yang Y, Wang J, Li LJ, Xu J, Ren TL - Sci Rep (2014)

The experimental results of the MoS2-Graphene-MoS2 FESBT (MGM-FESBT).(a) Schematic structure of the MGM-FESBT based on two graphene-MoS2 heterojunctions. (b) Optical image of the MGM heterojunction with few-layer MoS2 film and few-layer graphene film deposited onto a 300 nm SiO2/Si substrate. (c) AFM image of the MGM heterojunction. (d) The current vs. bias voltage characteristics of MGM-FESBT at various Vgate. The black arrow indicates the direction of increasing Vgate. (e) The current vs. gate voltage characteristics of MGM-FESBT at various Vbias. (f) The current vs. bias voltage characteristics demonstrating how current can be rectified by changing Vgate.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4127518&req=5

f3: The experimental results of the MoS2-Graphene-MoS2 FESBT (MGM-FESBT).(a) Schematic structure of the MGM-FESBT based on two graphene-MoS2 heterojunctions. (b) Optical image of the MGM heterojunction with few-layer MoS2 film and few-layer graphene film deposited onto a 300 nm SiO2/Si substrate. (c) AFM image of the MGM heterojunction. (d) The current vs. bias voltage characteristics of MGM-FESBT at various Vgate. The black arrow indicates the direction of increasing Vgate. (e) The current vs. gate voltage characteristics of MGM-FESBT at various Vbias. (f) The current vs. bias voltage characteristics demonstrating how current can be rectified by changing Vgate.
Mentions: A novel MoS2-graphene-MoS2 FESBT (MGM-FESBT) is also demonstrated, which has an ability to rectify a current by changing the gate voltage. As shown in Figure 3a, the structure of the MGM-FESBT consists of two GMHs. Optical microscopy (Figure 3b) and AFM images (Figure 3c) show the structure of the MGM heterojunction. The thicknesses of the two MoS2 flakes are 40 nm and 24 nm, respectively. The graphene flake is 28 nm thick. The electrical characteristics of the two MoS2-graphene junctions show some differences (Supporting Figure S5) due the difference of thicknesses of MoS2 in two GMHs. The working principle of the MGM-FESBT can be described as follows. A large amount of electrons inject from the drain terminal to MoS2 and then drift into the graphene. Due to the schottky barrier between MoS2-graphene and the recombination with holes in graphene, only a fraction of the injected electrons can pass through the graphene and be collected by the MoS2 at the source terminal. As the work function of the graphene is tunable by the gate voltage, the Schottky barrier between MoS2-graphene could be tuned from the gate to improved contact. Figure 3d shows the current vs. bias voltage characteristics of MGM-FESBT at various Vgate. The black arrow indicates the direction of increasing Vgate. It indicates that the lower gate voltage can lead to a higher Schottky barrier height between MoS2 and graphene. Figure 3e shows the current vs. gate voltage characteristics of a MGM-FESBT at various Vbias. Figure 3f demonstrates that the barrier property of a MGM-FESBT is tunable by Vgate. At Vgate = −10 V, the Schottky contact is formed in the MGM. After the gate voltage is increased to 42 V, the contact barrier is lowered. This means that the MGM can realize a “diode” to “resistor” transition easily, which may open a wide application space in next generation electronics.

Bottom Line: Recently, two-dimensional materials such as molybdenum disulphide (MoS2) have been demonstrated to realize field effect transistors (FET) with a large current on-off ratio.Moreover, the field effective mobility of the FESBT is up to 58.7 cm(2)/V · s.Our theoretical analysis shows that if the thickness of oxide is further reduced, a subthreshold swing (SS) of 40 mV/decade can be maintained within three orders of drain current at room temperature.

View Article: PubMed Central - PubMed

Affiliation: 1] Institute of Microelectronics, Tsinghua University, Beijing 100084, China [2] Tsinghua National Laboratory for Information Science and Technology (TNList), Tsinghua University, Beijing 100084, China [3].

ABSTRACT
Recently, two-dimensional materials such as molybdenum disulphide (MoS2) have been demonstrated to realize field effect transistors (FET) with a large current on-off ratio. However, the carrier mobility in backgate MoS2 FET is rather low (typically 0.5-20 cm(2)/V · s). Here, we report a novel field-effect Schottky barrier transistors (FESBT) based on graphene-MoS2 heterojunction (GMH), where the characteristics of high mobility from graphene and high on-off ratio from MoS2 are properly balanced in the novel transistors. Large modulation on the device current (on/off ratio of 10(5)) is achieved by adjusting the backgate (through 300 nm SiO2) voltage to modulate the graphene-MoS2 Schottky barrier. Moreover, the field effective mobility of the FESBT is up to 58.7 cm(2)/V · s. Our theoretical analysis shows that if the thickness of oxide is further reduced, a subthreshold swing (SS) of 40 mV/decade can be maintained within three orders of drain current at room temperature. This provides an opportunity to overcome the limitation of 60 mV/decade for conventional CMOS devices. The FESBT implemented with a high on-off ratio, a relatively high mobility and a low subthreshold promises low-voltage and low-power applications for future electronics.

No MeSH data available.


Related in: MedlinePlus