Novel Metal Oxide Deposition Method to Fabricate Nanostructures

Mansouri, Robab*,**; Sandooghchian, Mehri**; Mansouri, Mohammad Reza**

* Department of Physic, University of Payame Noor, kooye Golestan, Shiraz, Iran, robabmansouri@yahoo.com

** Kerman Semiconductor Company, Flat no.7, building no25, Sarve Sharghi BLVD., Sa’adat Abad, Tehran-Iran, info@kermansem.com

Abstract

ZnO is well promised for applying in semiconductor nanodevices. In recent years, wide types of various nanostructures were interested and investigated. In this work, we constructed new designed CVD set up (Chemical Vapor Deposition) and then studied about ZnO nanostructures grown on a SnO2 deposited on a Si wafer, which was deposited by a new method of deposition, to find more sensitivity and selectivity than other nanostructures for applying in gas sensors. SnO2 is one of the nanomaterials, which is well promised to apply in gas sensors and ZnO too. Likely by applying both of them on a Si wafer, to achieve more sensitivity and selectivity.

Key Words: metal oxide, deposition, ZnO naopillar

1. Introduction

Semiconducting metal oxide have been extensively studied due to their simplicity, sensitivity and applicability in many field. Zinc oxide (ZnO), a n-type metal oxide semiconductor sensing material with a wide band gap (Eg = 3.37 eV at 300 K) and the exciton binding energy of 60 meV, much larger than those of other semiconductors, has been under extensive research owing to its high chemical stability, low cost, and good flexibility in fabrication. Most of the studies up to now are focused on sintered particle or thin-film based devices. Several groups have recently proposed that the nanowires, nanotetrahedral or nanoribbons of semiconducting oxides are very promising sensors, diodes and transistors and some of their results have shown that the devices based on one-dimensional nanostructures have great potential in overcoming the fundamental limitations.

To enhance these properties of nanostructures, we determined to prepare some depositions, such as stannous oxide, zirconium oxide and cobaltous oxide and then growth various nanostructures on them. Here we fabricated only nanostructures of zinc oxide on SnO2 deposited layer.

Deposition of metals and metal oxides render new

properties to nanostructures and were interested by scientists. For example, by proper deposition, new properties are rendered to a nanostructure.

Depositions have been executed by sputtering method so far. It has own advantages and disadvantages on quality of layer. It needs a strong vacuum and it is extremely extortionate specially for wide areas, for example, by this method it is impossible and very expensive to deposit 1 m2.

By this project, we innovated new approach of deposition of metal oxide layer and executed with stannous oxide on type n of Si wafer to fabricate ZnO nanostructures first, and developed later by other metals. By this method, we could fabricate aligned nanowire of ZnO. Early aligned ZnO nanowire was fabricated on gold-deposited Si wafer and it was expensive.

This new method gives some advantages like Easy process, cheap process, low waste, and fabricating some new nanostructures, for example aligned nanowire of ZnO by deposition of gold has been fabricated in pervious. It gives us an opportunity to have various depositions with cheap and easy process.

2. Experiment

At the out set we prepared Stannous oxide layer on type n of 100 Si wafer by the following explained method. Then we innovated and constructed a new designed CVD set up and after the very zinc oxide nanostructures were fabricated on the very deposited Si wafer by new constructed CVD set up. At terminally stage the sample was investigated by SEM (scanning electron microscope), EDX (electron diffraction X-ray) and chemical analysis. The each single of steps are explained individually by detail.

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As well as known, SnO2 has orthorhombic crystal structure and during regeneration of deposited layer of SnCl2 solution Sn molecules is laid on Si atoms in flat style by its hexagonal bases. It is supposed that very layer which bounded with Si atoms forms a pattern to growth. The hexagonal of SnO2 layer act as a pattern to align growing and it is proven by SEM images in figs 2and 5.

It seems that the SnO2 layer remain on Si wafer surface during the growth because EDX analysis shows Sn peak. Addition, after removing the nanostructures from wafer by ultrasonic the SnO2 metallic surface of layer is appeared.

However, this new method arise some advantages, which are brought following:

• Easy and cheap process

• Low waste

• Fabricating some new nanostructures, for example aligned nanowire of ZnO by deposition of gold has been fabricated in pervious.

4. Acknowledgment

These schievment would not have been possible without sustained efforts of Narges Arampasand, Morteza Bayati, Ali Sanee and R. Rahimi.

5. References

[1]. Ki-Won Kim, Pyeong-Seok Cho, Sun-Jung Kim, Jong-Heun Lee, Chong-Yun Kang, Jin-Sang Kim, Seok-Jin Yoon “The selective detection of C2H5OH using SnO2–ZnO thin film gas sensors prepared by combinatorial solution deposition” Sensors and Actuators B 123 (2007) 318–324.

[2]. Ji. Haeng Ya. Gyoong, Man. Choa; “Selective CO gas

Delection of CuO- and ZnO doped Sno2 gas sensor”Sensors and Actuators B 75 (2001) 56-61.

NSTI-Nanotech 2010, www.nsti.org, ISBN 978-1-4398-3401-5 Vol. 1, 2010650