Pulsed Laser Deposition: Introduction

Posted on June 15, 2012

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In 1960 Theodore Maiman developed, demonstrated and patented the first laser, using a pink ruby medium and a helical gas discharge flashtube for optical pumping, at the Hughes Research Laboratory.

Following Maiman’s break-through, theoretical and experimental studies were carried out on the interaction of lasers with solid, liquid and gaseous materials. The ease with which material could be vaporised led to Smith and Turner demonstrating the first deposition of a thin film using intense laser radiation in 1965.

Pulsed laser deposition (PLD) is a physical vapour process, carried out in a vacuum system. A pulsed laser is focused on a target of the material to be deposited. For sufficiently high laser density, each laser pulse ablates a small amount of the material, which is ejected from the target in a highly forward-directed plasma plume. This ablation plume provides the material flux for film growth.

Typical Schematic for Pulsed Laser Deposition Process

In the 1970’s, the development of electronic Q-switching, a technique by which a laser can be made to produce a short pulsed output beam of power exceeding 108 Wcm-2, and of a high efficiency second harmonic generator to deliver shorter wavelength radiation, led to a wider scope for material selection and improved film quality. It was not until the 1980’s, with the growth of high temperature superconducting films in 1987 by Venkatesan, that interest in the field of pulsed laser deposition really started to grow.

Today PLD is used in the deposition of insulators, semiconductors, metals, polymers and biological materials. PLD has many attractive features which make it favourable for film growth. These include stoichiometric transfer of material from the target, generation of energetic species, hyperthermal reaction between the ablated cations and background gas in the ablation plasma, and the compatibility with background pressures ranging from ultra high vacuum (UHV) to 1 Torr. PLD also offers shot-to-shot control of the deposition process, which makes it ideal for situations in which monolayer control is needed. This is due to the fact that the film growth per laser pulse depends on controllable factors such as target-substrate distance, background gas pressure, laser spot size and laser energy density. The deposition rate per laser pulse under typical conditions can range from 0.001 to 1Å.

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