Deposition: Pulsed Laser Deposition System

EMSL's pulsed laser deposition (PLD) system is specially designed for epitaxial growth of oxide, ceramic, or synthetic mineral thin films. The system is composed of the following:

• An electro-polished stainless steel chamber pumped via a turbo molecular pump and backed by a rotary scroll dry pump
• An excimer laser (KrF) for excitation at 248 nm
• Three standard mass flow control units for precise and reproducible process gas during deposition
• An electron cyclotron resonance (ECR) plasma gas source
• Reflection high-energy electron diffraction (RHEED) for real-time monitoring of the surface structure and morphology
• A continuous compositional spread control system for combinatorial synthesis utilizing up to three different targets.

The PLD system is capable of growing uniform, multilayer, or compositionally spread combinatorial complex-oxide thin films with abrupt interfaces.

System Configuration and Operational Overview

Ablation plume during PLD deposition

PLD sample chamber

The PLD system is custom designed and manufactured by PVD Products Inc., and loosely based on the NanoPLD™ system, which has been modified to include microwave plasma assistance and in-situ film growth monitoring capabilities. The ultrahigh vacuum (UHV) multi-target manipulator holds up to six individual targets ranging from 25 mm to 52 mm in diameter, provides continuous target rotation up to 40 RPM, and provides target indexing operated either manually, or with a computer controlled motor. A water-cooled top shield reduces the radiative thermal load on the targets, as well as the manipulators, gears, and bearings.

Synchronizing the positioning and rotation of the target carousel with the substrate rotation allows the formation of a continuously varying composition across the sample surface for combinatorial synthesis using up to three separate targets. PLD utilizing a multi-target carousel is particularly suitable for multi-component oxide thin films, complex oxides, multilayers, delta-doping, and combinatorial thin films.

Plasma-assisted laser molecular beam epitaxy (OPALMBE) can be performed in the PLD system using an ECR gas plasma source. The system has six target holders and four individual gas source lines. The sample manipulator will hold one two-inch diameter substrate or multiple small samples, allowing the opportunity to coat a variety of substrate sizes and shapes.

The maximum growth temperature is about 1000° C in up to 1 atm oxygen for non-transparent substrates and 950° C for transparent substrates with no thermal paste or bonding required. The working base pressure of the growth chamber is lower than ~1x10-8 torr owing to the porosity and outgassing of multiple ceramic targets and also the Intelligent Window™. The Intelligent Window keeps the optical beam path clear over multiple sample depositions extending the longevity of the optical window from 20 to 50 times longer. Coupled with a loadlock for easy sample entry, the Intelligent Window allows for extended use periods absent venting for maximum cleanliness.

A sophisticated computer control system enables flexible and reproducible growth of thin films, heterostructures, multilayers, and compositional spread samples. The computer control system allows control of target motion, substrate rotation, substrate temperature, MFC flow rates, pressure, Intelligent Window, laser functions, and laser beam rastering. Surface structure, morphology, and growth rate can be monitored in real-time by high pressure (RHEED) at pressures up to ~50 mtorr with the TorrRHEED™ system by STAIB Instruments.

Individuals can use this instrument independently for their research after discussions with scientific contacts listed below.

Microwave Plasma Unit

PLD system and excimer laser

The plasma unit is an UHV compatible plasma source (PCS-ECR) for the generation of atoms and ions from SPECS. Through the action of the ECR phenomenon, a high-density plasma is created by coupling a radially symmetric 2.45-GHz microwave field to ions on the 86-mT surface of a multi-polar magnetic array. The absence of a hot filament to create the plasma permits operation with most gases, including oxygen, nitrogen, and hydrogen. This plasma unit is equipped for use as an atom/ion hybrid source with electrodes for the extraction of variable kinetic energy ions from the plasma.

Excimer Laser

The KrF pulsed laser is a medium, average power laser for material processing, science, and medical systems from Lambda Physik (Model COMPexPro 102), which emits 248 nm light. Operation is made simple with a handheld keypad that includes user-friendly function keys and a LCD display. Integration into the PLD system control software is accomplished through the standard RS232 remote port. The use of a fully contained, interlocked protective housing allows safe operation of the laser by preventing the possibility of exposure of the eye or skin.

All Related Publications Related Publications

1. Crystal and Electronic Structure of Lithiated Nanosized RutileTiO2 by Electron Diffraction and Electron Energy-loss Spectroscopy.
2. Origin of two time-scale regimes in potentiometric titration of metal oxides. A replica kinetic Monte Carlo study.
3. Role of Directed van der Waals Bonded Interactions in the Determination of the Structures of Molecular Arsenate Solids.
4. Simple Kinetic Monte Carlo Models for Dissolution Pitting Induced by Crystal Defects.
5. Shared and closed-shell O-O interactions in silicates.