研究目的
To demonstrate a method to reversibly induce point ripples in electrically isolated few-layer graphene and measure the change in transport properties, confirming that microscopic corrugation changes can solely account for graphene's non-ideal charge-carrier mobility.
研究成果
The study demonstrates that electrostatic manipulation can be used to repeatedly separate out layers of few-layer graphene, and measure the change in transport as local point ripples are formed and stretched. These increasing resistances resulting from microscopic corrugations are large enough to account for reported low charge carrier mobility in graphene. The method can be extended to study other rippling effects including mechanical properties, the formation of electron-hole puddles and the formation of a band gap.
研究不足
The lateral extension of the graphene manipulation is unknown, making quantitative determinations of the locally-induced strain or loading not possible. There is some ambiguity when the layers numbers go above 4, but for n ≤ 4 the method is complimentary to Raman and AFM for counting the number of layers in graphene.
1：Experimental Design and Method Selection:
The study uses a multi-probe method with local probe electrostatic manipulation to controllably and reproducibly perturb mechanically exfoliated few-layer graphene creating a localized ripple or wrinkle in the layers while simultaneously measuring resistance.
2：Sample Selection and Data Sources:
Graphene samples were prepared by mechanical exfoliation of highly-oriented pyrolytic graphite on to the surface of a 90 nm SiO2 layer on Si. Flakes containing few-layer graphene were identified initially by scanning electron microscopy (SEM) and then confirmed by Raman spectroscopy and AFM.
3：List of Experimental Equipment and Materials:
Samples were annealed at 200 °C for an hour in ultra-high vacuum (UHV), within an Omicron multi-probe system. Tips were electrochemically etched from tungsten and annealed in the UHV chamber to remove surface oxide.
4：Experimental Procedures and Operational Workflow:
The right probe is biased to ±0.1 V, ±0.2 V and ±0.5 V, and moved towards and away from the graphene in the z-direction perpendicular to the graphene layer at a constant speed ten times for every voltage.
5：1 V, ±2 V and ±5 V, and moved towards and away from the graphene in the z-direction perpendicular to the graphene layer at a constant speed ten times for every voltage.
Data Analysis Methods:
5. Data Analysis Methods: The measured current response is fitted to a network model to measure in-plane and cross-plane sheet resistance increases due to the locally-induced ripple in the graphene.
独家科研数据包，助您复现前沿成果，加速创新突破
获取完整内容
