Preparation and Characterization of C60/Graphene Hybrid Nanostructures

Summary

Here we present a protocol for the fabrication of C₆₀/graphene hybrid nanostructures by physical thermal evaporation. Particularly, the proper manipulation of deposition and annealing conditions allow the control over the creation of 1D and quasi 1D C₆₀ structures on rippled graphene.

Abstract

Physical thermal deposition in a high vacuum environment is a clean and controllable method for fabricating novel molecular nanostructures on graphene. We present methods for depositing and passively manipulating C₆₀ molecules on rippled graphene that advance the pursuit of realizing applications involving 1D C₆₀/graphene hybrid structures. The techniques applied in this exposition are geared towards high vacuum systems with preparation areas capable of supporting molecular deposition as well as thermal annealing of the samples. We focus on C₆₀ deposition at low pressure using a homemade Knudsen cell connected to a scanning tunneling microscopy (STM) system. The number of molecules deposited is regulated by controlling the temperature of the Knudsen cell and the deposition time. One-dimensional (1D) C₆₀ chain structures with widths of two to three molecules can be prepared via tuning of the experimental conditions. The surface mobility of the C₆₀ molecules increases with annealing temperature allowing them to move within the periodic potential of the rippled graphene. Using this mechanism, it is possible to control the transition of 1D C₆₀ chain structures to a hexagonal close packed quasi-1D stripe structure.

Introduction

This protocol explains how to deposit and manipulate C₆₀ molecules on graphene such that 1D and quasi-1D C₆₀ chain structures can be realized. The techniques in this experiment were developed to address the need to guide adsorbates into desirable configurations without having to rely on manual manipulation, which is slow and can require great effort. The procedures described here rely on the use of a high vacuum system with a sample preparation area capable of supporting molecular deposition and thermal annealing of the samples. STM is used to characterize the samples, but other molecular resolution techniques may be applied.

Protocol

1. Preparation of the Homemade Knudsen Cell

1. Prepare components for Knudsen cell
   1. Purchase a CF flanged based power feedthrough (2.75" CF, 4 pins stainless steel). Drill two threaded holes through the feedthrough, at the cross points between one diameter 1.30" line and its circumference.
   2. Prepare a glass tube (0.315" outside diameter (OD), 2.50" length).
   3. Purchase thin copper sheets (99.9%) with 0.005" thickness. Cut one sheet to the dimensions of 7.5" L x 5.0" W using a pair of scissors, then curl it to a hollow columniform shield with a 1.45" diameter by hand (

Results

Following evaporation, the graphene with the newly deposited C₆₀ is annealed at 150 °C for 2 h. The large-scale STM image in Figure 2a shows a characteristic quasi-1D C₆₀ chain structure found after this initial annealing process. A closer inspection in Figure 2b reveals detailed information of this 1D structure, in which each bright spherical protrusion represents one single C₆₀ molecule. Typical.......

Discussion

The techniques described in this protocol are designed for thermal deposition of organic materials and other high vapor pressure materials. These techniques can be integrated with ultra-high vacuum systems that have sample preparation areas capable of supporting molecular evaporation as well as thermal annealing. The aim for this specific experiment is to deposit C₆₀ molecules on graphene substrate and study the self-assembly of C₆₀ and the thermal effect.

The benefit of .......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
CF Flanged power feedthrough	Kurt J. Lesker	EFT0042033
Copper sheets	Alfa Aesar	7440-50-8
Thermocouple chromel/alumel wires	Omega Engineering	ST032034/ST080042
Tungsten wires	Alfa Aesar	7440-33-7
Stainless steel rods	McMaster-Carr	95412A868
Copper wires	McMaster-Carr	8873K28
Hollow copper rods	McMaster-Carr	7190K52
C60	MER Corporation	MR6LP