Laser ablation assisted deposition

The requirements of thin-film ferroelectrics are stoichiometry, phase formation, crystallization, and microstmctural development for the various device appHcations. As of this writing multimagnetron sputtering (MMS) (56), multiion beam-reactive sputter (MIBERS) deposition (57), uv-excimer laser ablation (58), and electron cyclotron resonance (ECR) plasma-assisted growth (59) are the latest ferroelectric thin-film growth processes to satisfy the requirements. 

Stephan was the first to attempted direct synthesis of the B and N multi walled carbon nanotubes (BCN-MWNTs) in 1994 [15-17]. Since then, considerable progress has been made in the synthesis of BCN-MWNTs by different means of arc-discharge [16-18], laser ablation [18-20], piyolysis methods [18,21], and chemical vapor deposition [18,20-24]. Aligned BNC nanotubes have been sueeessfully fabricated by bias assisted hot filament chemieal vapor deposition [27,28]. Up to now, the only existing BCN-SWNTs synthesis was achieved via an... 

During the last decade, processing of polymers has become an important field of applied and fundamental research [48]. One of the most important fields is laser ablation involving various techniques and applications. Laser ablation is used as an analytical tool for MALDI (matrix-assisted laser de-sorption/ionization) [28, 29] and LIBS (laser-induced breakdown spectroscopy) [49] or as a preparative tool for PLD (pulsed laser deposition) of inorganic materials [37] and of synthetic polymer films [50, 51]. Another application is surface modification of polymers [52] if low fluences are applied, the polymer surface can be either chemically modified to improve adhesion... 

Since its discovery, laser polymer processing has become an important field of applied and fundamental research. The research can be separated into two fields, the investigation of the ablation mechanism and its modeling and the application of laser ablation to produce novel materials. Laser ablation is used as an analytical tool in matrix-assisted laser desorption/ionization (MALDI) [12,13] and laser-induced breakdown spectroscopy (LIBS) [14] or as preparative tool for pulsed laser deposition (PLD) of synthetic polymers [15,16] and of inorganic films [17,18],... 

Two recent techniques that have come to be applied to compound semiconductors and oxides are pulsed laser deposition (PLD) also known as laser ablation [6] and ion beam assisted deposition (IBAD) [2-8]. These techniques have been developed for films whose elemental constituents are not easily volitalized in elemental or organome-tallic forms or whose formation can benefit from the added energy imparted to the reactants by the process. 

Several attempts have been made to synthesize thin film C3N4, be it cubic or hexagonal. These include reactive magnetron sputtering [184-187], laser ablation [188] ion beam assisted deposition (IBAD) [189], plasma [191, 192] and plasma-enhanced chemical vapour deposition [190]. 

Many methods have been reported for production of nanodiamonds (NDs) such as laser ablation, " plasma-assisted chemical vapor deposition," autoclave synthesis from supercritical fluids, ion irradiation of graphite, chlorination of carbides, electron irradiation of carbon onions, and ultrasound cavitation. Smaller NDs can be prepared by detonation processes that yield aggregates of NDs with sizes of 4-5 nm embedded in a detonation soot composed of other carbon allotropes and impurities. An explosive mixture having an overall negative oxygen balance provides a source of both carbon and energy for the conversion. Because of their small size (2-10 nm) detonation NDs have also been referred to as ultradispersed, nanocrystalline... 

Cubic BN can also be obtained at low pressure in the field of stability of h-BN under nonequilibrium conditions, in analogy to the formation of diamond or diamond-Hke carbon films. As in the case of diamond, CVD, plasma-assisted chemical vapor deposition (PACVD), and PVD methods such as ion beam bombardment, radiofrequency sputter deposition, laser ablation, and magnetron sputtering can each be appHed. 

Applications employing laser ablation of polymers include film deposition and the synthesis of certain organic compounds. Laser beam ablation in conjunction with mass spectrometry is an important tool for polymer analysis, which is referred to as laser desorption mass spectrometry (LDMS). One particular type of LDMS, termed matrix-assisted laser desorption/ionization (MALDI), has contributed essentially to the analysis of proteins (Nobel prize for chemistry to K. Tanaka in 2002) [126,127]. Further information on this subject is available in Ref [4]. 

Laser Desorption/Ablation Ionization Methods. Matrix-assisted laser desoiption ionization (MALDI) relies on the use of a solid chromophQric matrix, chosen to absorb laser light, which is co-mixed with the analyte (4). Typically, a solution of a few picomoles of analyte is mixed widi a lOO-to-5000 fold excess of the matrix in solution. A few microliters of the resulting solution are deposited on a mass spectrometer solids probe, and the solvent is allowed to evaporate before inserting the probe into the mass spectrometer. When the pulsed laser beam strikes the sample surface in the spectrometer, the sample molecules are desorbedAonized at high efficiency. The various mechanisms for matrix and non-matrix assisted laser desorption have been discussed (5,6). 

Matsubara et al. [126] used oxygen radical-assisted PLD to grow highly transparent and low-resistivity Al-doped ZnO films at room temperature. A KrF excimer laser (X = 248 nm, 30 ns pulse width, 10 Hz repetition rate) was used for ablation. The oxygen partial pressure during deposition was 0.7-1.4 x 10 Torr, and the applied RF power was 150W. The distance between the target and the substrate was approximately 6 cm. The minimum resistivity of the obtained transparent films was... 

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