Sputtering, physical elements

In contrast, physical techniques of thin film synthesis are based upon evaporation or sputtering of elemental or multicomponent sources and subsequent deposition of this material onto a substrate molecular precursors do not play a significant role in thin film synthesis via these techniques. Examples of physical techniques used to prepare thin films include (1) Molecular Beam Epitaxy (2) sputtering, ... 

R. Behrisch, ed., "Sputtering by Particle Bombardment I Physical Sputtering of Single Element SoHds," in Topics inMppliedPhjsics, Vol. 47, Springer-Vedag, Berlin, 1981. 

The limitations of SIMS - some inherent in secondary ion formation, some because of the physics of ion beams, and some because of the nature of sputtering - have been mentioned in Sect. 3.1. Sputtering produces predominantly neutral atoms for most of the elements in the periodic table the typical secondary ion yield is between 10 and 10 . This leads to a serious sensitivity limitation when extremely small volumes must be probed, or when high lateral and depth resolution analyses are needed. Another problem arises because the secondary ion yield can vary by many orders of magnitude as a function of surface contamination and matrix composition this hampers quantification. Quantification can also be hampered by interferences from molecules, molecular fragments, and isotopes of other elements with the same mass as the analyte. Very high mass-resolution can reject such interferences but only at the expense of detection sensitivity. 

The experimental data presented confirm that - at least after the disappearance of the smallest elements at the beginning of the sputtering - the particle sizes can indeed be adjusted by the applied ion dose, which allows us to follow the size dependent changes of the physical properties of the particles from the bulk limit. 

Anderson, H. H. Bay, H. L. in Sputtering by Particle Bombardment 7, Physical Sputtering by Single-Element Solids Behrish, R., Ed. Springer-Verlag Berlin. 1981 Chapter 4. 

The relevance of chemical erosion became evident when introducing low Z elements, in particular carbon, for plasma facing components in tokamaks. The erosion yields of chemical processes and sputtering can be of the same order of up to a few percent but show significantly different dependencies physical sputtering has a strong j-dependence, whereas the yield Ych of chemical erosion varies with surface temperature Ts and flux density, as is shown in the following. 

Physical Sputtering 9.2.1 Sputtering of Pure Elements Kinetic Effects... 

The basic structure of polycrystalline cadmium telluride (CdTe) thin-film cells has a glass superstrate and a layer of TCO as front contact, a near-transparent n-type cadmium sulfide (CdS) window layer, p-type CdTe, and a metallic rear contact. The CdTe is usually deposited by three families of techniques. In the first group (vapor transport deposition, close space sublimation, physical vapor deposition, and sputtering) elemental vapors of Cd and Te condense and react on the substrate. In the second (electrodeposition), Cd + and HTe02" ions in acidic electrolyte are galvanically reduced at the surface ... 

Andersen, H.H., Bay, H.L. Sputtering yield measurements. In Behrisch, R. (ed.) Sputtering by Particle Bombardment. I. Physical Sputtering of Single Element Solids, Topics in Applied Physics, vol. 47, pp. 145-218. Springer, Berlin (1981)... 

SIMS is used for quantitative depth profile determinations of trace elements in solids. These traces can be impurities or deliberately added elements, such as dopants in semiconductors. Accurate depth prohles require uniform bombardment of the analyzed area and the sputter rate in the material must be determined. The sputter rate is usually determined by physical measurement of the crater depth for multilayered materials, each layer may have a unique sputter rate that must be determined. Depth prohle standards are required. Government standards agencies like NIST have such standard reference materials available for a limited number of applications. For example, SRM depth profile standards of phosphorus in silicon, boron in silicon, and arsenic in silicon are available from NIST for calibration of SIMS instmments. P, As, and B are common dopants in the semiconductor industry and their accurate determination is critical to semiconductor manufacture and quality control. 

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