Plan-View TEM Specimen Preparation for Atomic Layer Materials Using a DB-FIB Approach

Apr 2016 – Oct 2017

Master Student
Department of Materials Science ⋅ National Taiwan University

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Mission
The inter-layer orientation and corresponding properties are intriguing topics for 2D atomic layer materials. However, its vulnerable nature makes it difficult to prepare specimens for plan-view TEM analysis. Our goal is to develop a zero-damage sample preparation approach suitable for 2D atomic layer materials.

My contribution
Idea proposer and project executor

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Main Achievement

• Invented a “MICROCAPSULE” plan-view TEM specimen preparation approach by using DB-FIB
• The approach is site-specific and can prevent from ion-induced damage and contamination; especially suitable for 2D atomic layer materials.
• Successfully applied to monolayer MoS₂ and graphehe with substrate-supported and free-standing
• Successfully applied to plan-view TEM analysis of multi-layer graphene; revealed contradictary results in Raman spectroscopy and TEM diffraction of graphene stacking types.

Schematic illustration of the components of the microcapsule used to protect atomic layers for plan-view specimen preparation by FIB milling.

SEM images of the microcapsule plan-view specimen preparation steps in a dual-beam FIB-SEM system. The scale bar is 5 μm.

Application to free-standing monolayer graphene. (a) 40-nm nitride membrane with penetrating holes, covered by monolayer graphene. (b) Zoom in SEM image in (a) clearly shows free-standing graphene. (c) Sample preparation by microcapsule approach. (d) The plan-view TEM speimen is mounted on Cu grid and well-prepared. The free-standing graphene lies in the window for TEM observation. (e) Zoom in SEM image in (d) shows the back side of free-standing graphene. The structure remains undisturbed after sample preparation if comparing with (b). (f) Selected-area electron diffraction pattern of free-standing graphene.

Application to substrate-supported multi-layer graphene. (a) SEM image of multi-layer graphene. The central region is covered by four layers of graphene and labeled as 4L. (b) Selected-area electron diffraction pattern of the plan-view specimen prepared from the four-layer region in (a).