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Uniformly Nanopatterned Graphene Field-Effect Transistors with Enhanced Properties.

Choi D, Kuru C, Kim Y, Kim G, Kim T, Chen R, Jin S - Nanoscale Res Lett (2015)

Bottom Line: We have successfully fabricated and characterized highly uniform nanopatterned graphene (NPG).Electronic characterization of single-layer NPG field-effect transistors (FETs) was performed, which demonstrated a high on-off switching ratio.We found that the NPG allows for experimental confirmation of the relationship between electrical conductance and bandgap.

View Article: PubMed Central - PubMed

Affiliation: Materials Science and Engineering, University of California, San Diego, La Jolla, CA, 92093, USA.

ABSTRACT
We have successfully fabricated and characterized highly uniform nanopatterned graphene (NPG). Thin anodized aluminum oxide nanomask was prepared by facile self-assembly technique without using polymer buffer layer, which was utilized as a direct-contact template for oxygen plasma etch to produce near-periodic, small-neck-width NPG. The NPG exhibits a homogeneous mesh structure with an average neck width as small as ~11 nm. The highly uniform 11-nm neck width creates a quantum confinement in NPG, which has led to a record bandgap opening of ~200 meV in graphene for the given level of neck width. Electronic characterization of single-layer NPG field-effect transistors (FETs) was performed, which demonstrated a high on-off switching ratio. We found that the NPG allows for experimental confirmation of the relationship between electrical conductance and bandgap. This work also demonstrates that our direct-contact, self-assembled mask lithography is a pathway for low-cost, high-throughput, large-scale nanomanufacturing of graphene nanodevices.

No MeSH data available.


Comparison of Raman spectra. a Before versus b after patterning NPG showing ~8 cm−1 blueshift on G band due to nanopatterning (11–13-nm neck width)
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Fig3: Comparison of Raman spectra. a Before versus b after patterning NPG showing ~8 cm−1 blueshift on G band due to nanopatterning (11–13-nm neck width)

Mentions: Raman spectroscopy was used as a nondestructive tool for probing the edge structure and the crystallinity of sp2-bonded graphene. Figure 3 demonstrates the Raman spectra of pristine graphene and NPG. The Raman data was taken from different spots on graphene to check the uniformity. Prior to patterning, the G (~1586 cm−1) and 2D (~2682 cm−1) bands were prominent. The D peak at ~1341 cm−1 is related to defects and disorder. This is forbidden in perfect graphitic systems and requires a defect for its activation, and so is observed at the edges of graphene samples [15–17]. The integrated intensity ratio of the D band and G band (ID/IG) is a parameter sensitive to defect density [17, 18]. In Fig. 3a, the high D peak was observed on porous graphene with the value of ID/IG increased by a factor of 3, which suggests that defects in our sample are significantly formed by nanopatterning and pore edge formation. After nanopatterning, there is a systematic upshift in the position of the G band. The G band position for porous graphene was observed at ~1594 cm−1, which can be compared with the G position of pristine graphene (~1586 cm−1) in our sample. This upshift in the G band position further confirms the hole doping in the NPG by the formation of oxygen dangling bonds with graphene, as reported by previous research [15]. We also note that there is an increase in the intensity ratio of the IG/I2D with more defects. The increase in the IG/I2D in NPG is due to the alteration of its electronic transformation from semimetallic to semiconducting with successive opening of bandgap [19].Fig. 3


Uniformly Nanopatterned Graphene Field-Effect Transistors with Enhanced Properties.

Choi D, Kuru C, Kim Y, Kim G, Kim T, Chen R, Jin S - Nanoscale Res Lett (2015)

Comparison of Raman spectra. a Before versus b after patterning NPG showing ~8 cm−1 blueshift on G band due to nanopatterning (11–13-nm neck width)
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4499035&req=5

Fig3: Comparison of Raman spectra. a Before versus b after patterning NPG showing ~8 cm−1 blueshift on G band due to nanopatterning (11–13-nm neck width)
Mentions: Raman spectroscopy was used as a nondestructive tool for probing the edge structure and the crystallinity of sp2-bonded graphene. Figure 3 demonstrates the Raman spectra of pristine graphene and NPG. The Raman data was taken from different spots on graphene to check the uniformity. Prior to patterning, the G (~1586 cm−1) and 2D (~2682 cm−1) bands were prominent. The D peak at ~1341 cm−1 is related to defects and disorder. This is forbidden in perfect graphitic systems and requires a defect for its activation, and so is observed at the edges of graphene samples [15–17]. The integrated intensity ratio of the D band and G band (ID/IG) is a parameter sensitive to defect density [17, 18]. In Fig. 3a, the high D peak was observed on porous graphene with the value of ID/IG increased by a factor of 3, which suggests that defects in our sample are significantly formed by nanopatterning and pore edge formation. After nanopatterning, there is a systematic upshift in the position of the G band. The G band position for porous graphene was observed at ~1594 cm−1, which can be compared with the G position of pristine graphene (~1586 cm−1) in our sample. This upshift in the G band position further confirms the hole doping in the NPG by the formation of oxygen dangling bonds with graphene, as reported by previous research [15]. We also note that there is an increase in the intensity ratio of the IG/I2D with more defects. The increase in the IG/I2D in NPG is due to the alteration of its electronic transformation from semimetallic to semiconducting with successive opening of bandgap [19].Fig. 3

Bottom Line: We have successfully fabricated and characterized highly uniform nanopatterned graphene (NPG).Electronic characterization of single-layer NPG field-effect transistors (FETs) was performed, which demonstrated a high on-off switching ratio.We found that the NPG allows for experimental confirmation of the relationship between electrical conductance and bandgap.

View Article: PubMed Central - PubMed

Affiliation: Materials Science and Engineering, University of California, San Diego, La Jolla, CA, 92093, USA.

ABSTRACT
We have successfully fabricated and characterized highly uniform nanopatterned graphene (NPG). Thin anodized aluminum oxide nanomask was prepared by facile self-assembly technique without using polymer buffer layer, which was utilized as a direct-contact template for oxygen plasma etch to produce near-periodic, small-neck-width NPG. The NPG exhibits a homogeneous mesh structure with an average neck width as small as ~11 nm. The highly uniform 11-nm neck width creates a quantum confinement in NPG, which has led to a record bandgap opening of ~200 meV in graphene for the given level of neck width. Electronic characterization of single-layer NPG field-effect transistors (FETs) was performed, which demonstrated a high on-off switching ratio. We found that the NPG allows for experimental confirmation of the relationship between electrical conductance and bandgap. This work also demonstrates that our direct-contact, self-assembled mask lithography is a pathway for low-cost, high-throughput, large-scale nanomanufacturing of graphene nanodevices.

No MeSH data available.