Thin Film Growth by Pulsed Laser Deposition
The use of Pulsed Iaver Deposition (PLD) to grow a variety of thin multicomponent films, including dielectric, protective, and superconducting layers, is described. The underlying principles governing the laser-target interaction and removal of material f
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Abstract The use ofPulsed Laser Deposition (PLD) to grow a variety ofthin multicomponent films, including dielectric, protective, and superconducting layers, is described. The underlying principles governing the laser-target interaction and removal ofmateria/from the i"adiated surface are briefly reviewed. Additionally, particular advantages and disadvantages ofthe technique are discussed, and future directions proposed.
Introduction Considerable attention has been extended to the application of laser radiation to initiate or enhance thin film growth over the past decade [1 ]. Dielectric, semiconductor, metal and superconductor films have been grown by a variety of processing modes involving photonic or thermal (or both) reactions induced by the quantised energy. One such technique currently attracting enormous interest is Pulsed Laser Deposition (PLD), particularly for multi-component thin film growth. Although dating back more than 28 years [2], the field burgeoned during the late 1980's principally because of the discovery the new families of layered cuprate superconductors. In fact, some of the best quality superconducting films currently available have been prepared by PLD. The subject of Pill is paper briefly introduced and reviewed here, indicating the numerous advantages and less desirable effects associated with the technique. The application towards the growth of interface dielectrics and protective layers suitable for a range of multilayer structures with semiconductors will be described, as well as the use of sandwiching methods to prepare BiPbSrCaCuO and PbSrYCaCuO super-conducting films. Finally, the potential for reactive Pill will be summarised.
Background and Theory Pulsed Laser Deposition is a conceptually simple technique involving the collection on a substrate of material removed from a pulsed laser-irradiated target. It offers many attractions. Material transfer is congruent (i.e. stoichiometry is preserved), atomic flux is easily regulated, novel layers and multilayers may be readily grown, and it is simple and relatively inexpensive. Over the years a wide variety of descriptive terms have been
W. Waidelich (ed.), Laser in der Technik © Springer-Verlag Berlin Heidelberg 1994
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Vacuum Pump
Window
Fig .1. Schematic of a typical set-up used for PLD.
associated with Pill, which has been referred to as laser evaporation [2-6], laser assisted deposition and annealing (LADA) [7) laser flash evaporation [8), laser assisted sputtering [9), laser MBE [10), hydrodynamic sputtering [11], laser ablation [12-14} laser ablation deposition [15], and laser evaporation deposition (LEDE) [16]. Figure 1 shows schematically a simple PLD arrangement for film growth. To make the process as efficient as possible, such that energy is not lost due to carrier or thermal diffusion during absorption, short laser pulses should be used at a wavelength strongly absorbed by the material. Lasers operable in the Q-switched mode, therefore, the Nd:Yag (1.0641Jm, 532nm, 355nm, 266nm), ruby (694nm), and excimers (XeCl a
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