Seedless Growth of Bismuth Nanowire Array via Vacuum Thermal Evaporation

Summary

A protocol for seedless and high yield growth of bismuth nanowire arrays through vacuum thermal evaporation technique is presented.

Abstract

Here a seedless and template-free technique is demonstrated to scalably grow bismuth nanowires, through thermal evaporation in high vacuum at RT. Conventionally reserved for the fabrication of metal thin films, thermal evaporation deposits bismuth into an array of vertical single crystalline nanowires over a flat thin film of vanadium held at RT, which is freshly deposited by magnetron sputtering or thermal evaporation. By controlling the temperature of the growth substrate the length and width of the nanowires can be tuned over a wide range. Responsible for this novel technique is a previously unknown nanowire growth mechanism that roots in the mild porosity of the vanadium thin film. Infiltrated into the vanadium pores, the bismuth domains (~ 1 nm) carry excessive surface energy that suppresses their melting point and continuously expels them out of the vanadium matrix to form nanowires. This discovery demonstrates the feasibility of scalable vapor phase synthesis of high purity nanomaterials without using any catalysts.

Introduction

Nanowires confine the transport of charge carriers and other quasiparticles, such as photons and plasmons in one dimension. Accordingly, nanowires usually exhibit novel electrical, magnetic, optical and chemical properties, which grant them nearly infinite potential for applications in micro/nano electronics, photonics, biomedical, environmental and energy-related technologies.^1,2 During the past two decades, numerous top-down and bottom-up approaches have been developed to synthesis a broad range of high quality metal or semiconductor nanowires at laboratory scale.^3-6 Despite of these developments, each approach relies on certain unique properti....

Protocol

Caution: Please consult all relevant material safety data sheets (MSDS) before use. Nanomaterials may have additional hazards compared to their bulk counterpart. Please use all appropriate safety practices when handling nanomaterial-covered substrates, including the use of engineering controls (fume hood) and personal protective equipment (safety glasses, gloves, lab coat, full length pants, closed-toe shoes).

1. Preparatory Work

1. Preparation of vapor deposition system
   1. Vent the deposition chamber to atmosphere pressure and open the chamber. The venting is done by pressing the "Start PC Venting" button on the control software inter....

Results

The cross-sectional SEM images of vanadium underlayers formed by magnetron sputtering and thermal evaporation methods are presented in Figure 2. Scanning electron microscopy (SEM) images are presented for bismuth nanowires formed at different substrate temperatures (Figure 3). The crystal structure of the bismuth nanowires is determined through transmission electron microscopy (TEM), selective area electron diffraction (SAED), and X-ray diffraction (XRD) studies (Figure 4

Discussion

The growth of bismuth nanowires is to be conducted in a physical vapor deposition system with at least two deposition sources, one for bismuth and another for vanadium. It is recommended that one of the sources is a magnetron sputtering source, for the deposition of vanadium. High vacuum is achieved by a turbomolecular pumps backed by a dry scroll pump. The vapor deposition system is equipped with a calibrated quartz crystal microbalance (QCM) for in situ thickness monitoring. The vapor deposition system has ele.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Bismuth	Sigma-Aldrich	556130	Granular, 99.999%
Vanadium Slug	Alfa Aesar	42829	3.175 mm (0.125 in) dia x 6.35 mm (0.25 in) length, 99.8%
Vanadium Sputtering Target	Kurt J. Lesker	EJTVXXX253A2	3.00" Dia. x 0.125" Thick, 99.5%
Acetone	Sigma-Aldrich	179124	>99.5%
Ethanol	Alfa Aesar	33361	Anhydrous
Silicon Wafer	University Wafers		300 microns in thickness, (100) orientation
Silver Filled Epoxy	Circuit Works	CW2400	Two part conductive epoxy resin
Tungsten Boat, Alumina Coated	R. D. Mathis	S9B-AO-W	For bismuth thermal evaporation
Tungsten Boat	R. D. Mathis	S4-.015W	For vanadium thermal evaporation
RIE Plasma	Nordson March	CS-1701
PVD 75 Vapor Deposition Platform	Kurt J. Lesker	PEDP75FTCLT001	Equipped with three thermal evaporation source and one DC magnetron sputtering source
Thermoelectric Temperature Controller	LairdTech	MTTC-1410
PT1000 RGD	LairdTech	340912-01	Temperature sensor for MTTC-1410
Thermoelectric Module	LairdTech	56910-502
Ultrasonicator	Crest Ultrasonics	Tru-Sweep 175