Sputtering Deposition of Metallic Thin Films Malcolm Clark, Sachin Muley, Paul M. Voyles Materials Science Program UW-Madison, Madison, WI, 53706, USA.

Introduction

Methods

Background

Summary Results

Sputtering is a method of physical vapor deposition used to deposit thin films. We have reconditioned a used vacuum system for sputtering deposition of metal thin films. Thin films microstructures varies with substrate temperature and pressure in which they are deposited.

1. Argon gas is bled into the vacuum chamber 2. A magnetic field traps free electrons which

ionize the gas molecules 3. As a result a plasma of the gas is formed 4. A magnetic field traps free electrons which

ionize the gas molecules 5. The energetically charged ions then collide

with the target knocking off atoms6. These atoms then coat the substrate making a

thin film

PurposeTo discover how the substrate temperature effects the structures and properties of thin films in order to create ultra-stable amorphous thin films for wear coatings

Sputtering Deposition• Used to fabricate the metallic thin films Scanning Electron Microscope • Used to analyze the topography and

composition of a sample by scanning it with a focused beam of electrons

XPS – X-ray Photoelectron Spectroscopy• Measures the elemental composition of a

material. This is used to find if there is any contamination or impurities in the thin film

How it works

References1. Materials Science Products. (n.d.). Retrieved from

https://www.sigmaaldrich.com/materials-science/material-science-products.html?TablePage=108832720

2. Hoffman, D. W., & McCune, R. C. (n.d.). Microstructural Control of Plasma-Sputtered Refractory Coatings. Handbook of Plasma Processing Technology, 483-517. Retrieved from http://www.atechsystem.co.kr/sub1/pdf/115.pdf

3. Thornton, J. A. (1974). Influence of apparatus geometry and deposition conditions on the structure and topography of thick sputtered coatings. J. Vac. Sci. Technol. Journal of Vacuum Science and Technology, 11(4), 666-670. doi:10.1116/1.1312732

4. Alfonso, E., Olaya, J., & Cubillos, G. (n.d.). Thin Film Growth Through Sputtering Technique and Its Applications. Retrieved from http://cdn.intechopen.com/pdfs/39143/InTech-Thin_film_growth_through_sputtering_technique_and_its_applications.pdf

Thornton Zone Diagram Zone 1 – loose fibrous grains Zone T – tightly packed fibrous grains Zone 2 – full dense columnar grains Zone 3 – recrystallization with random orientation

Future Work

Implications

1. Materials Science Products. (n.d.). Retrieved from https://www.sigmaaldrich.com/materials-science/material-science-products.html?TablePage=108832720

Aluminum Sample

• Aluminum films -Grow films at different substrate temperatures

• Zinc Films – grow zinc films at different homologous temps with the same argon pressure and compare them to aluminum film samples

• Explore substrate temperatures and argon pressures that maximize the stability of thin films

• Maintenance and upgrades of deposition system

T/Tm ≈ .32 (room temp)Argon Pressure 3.0 mTorr

T/Tm ≈ .3Argon Pressure 3.0 mTorr

T/Tm ≈ .5Argon Pressure 3.0 mTorr

T/Tm≈ .7Argon Pressure 3.0 mTorr

Expected outcomes for continued research

Films at deposited around these parameters will likely have tightly dense columnar grains that may extended through most of the film and a topography that consist of domed and faceted structures

It is reasonable for films at this homologous temperature and pressure to have fully dense columnar grains that extend through the entire film and to have a surface composed of faceted structures

A film fabricated at this homologous temperature and pressure is expected to have tightly packed fibrous grains and it would be expected to see smooth domed surface

Objective To reproduce results from literature – successful reproduction of results ensures that the sputtering deposition system functions properly

Plan Of Approach

To grow elemental films at different homologous temperatures at the same argon pressure. Then analyze the films and compare them to results from literature

Thornton Zone Diagram The Thornton Zone Diagram is a schematic showing the dependence of coating structure of the substrate temperature and argon pressure

Once all of the aluminum film samples are fabricated we will be able to analyze them and compare them to results from literature. If the samples match the results from literature we can confirm that the sputtering deposition system is working properly. We can then use the deposition system to examine substrate temperature and argon pressures that maximize the stability of thin films in order to create ultra-stable amorphous thin films for wear coatings.

At Homologous temperatures around .8 and above will begin to recrystallize and will have smooth flat grains at the surface with clear grooved boundaries.

T/Tm≈ .8

Wear Coatings Using sputtering deposition thin films can be created with unique properties and structures that make them optimal for wear coatings. Thin films Thin Film Properties • Corrosion resistant • Scratch resistant • Increased Hardness• Low friction Uses • Tool industry • Automotive industry

3. Thornton, J.A.

3. Thornton, J.A.

3. Thornton, J.A.

1. Hoffman, D. W., & McCune, R. C. (n.d.). Microstructural Control of Plasma-Sputtered Refractory Coatings. Handbook of Plasma Processing Technology, 483-517. Retrieved from http://www.atechsystem.co.kr/sub1/pdf/115.pdf

2. Hoffman, D. W., & McCune, R. C.