Thin films deposition methods

After the precursor stock solution is prepared, various techniques can be used to coat the substrate, depending on the solution viscosity, required film thickness and coverage. The most common methods in the semiconductor industry are spin- and dip-coating. Other processes that are used for deposition include spray coating and stamping. A summary of the uses, limitations, and advantages of the various thin film deposition methods is reported in Table 2.2. 

In the short term, there is a need to reduce the cost of thin-film solar cells. To do this will require the development of deposition techniques of thin films such as microcrystalline silicon and other materials that are robust and provide high throughput rates without sacrificing film efficiencies. In the short run, thin-film deposition methods can potentially gain... 

Electrochemical atomic layer epitaxy (EC-ALE) is the combination of underpotential deposition (UPD) and ALE. UPD is the formation of an atomic layer of one element on a second element at a potential under, or prior to, that needed to deposit the element on itself [5, 6]. The shift in potential results from the free energy of the surface compound formation. Early UPD studies were carried out mostly on polycrystalline electrode surfaces [7], This was due, at least in part, to the difficulty of preparing and maintaining single-crystal electrodes under well-defined conditions of surface structure and cleanliness [8]. The definition of epitaxy is variable but focuses on the formation of single crystal films on single crystal substrates. This is different from other thin film deposition methods where polyciystalline or amorphous film deposits are formed even on single crystal substrates. Homoepitaxy is the formation of a compound on itself. Heteroepitaxy is the formation of a compound on a different compound or element and is much... 

CVD is a well-understood thin film deposition method that uses chemical reactions of vapor-phase precursors. CVD processes have traditionally been initiated and controlled by heat as the source of energy. An elevated deposition temperature is normally required, which restricts the types of substrates that can be used and coating materials that can be deposited, especially thermally sensitive ones (Jones and Hitchman, 2009). However, thermal energy is not the only energy supplied to the system plasmas and photons are widely used in CVD processes. Plasma-enhanced chemical vapor deposition (PECVD), or plasma-assisted CVD, is a CVD technique in which plasma in lieu of thermal energy is used primarily to activate ions and radicals in the chemical reactions leading to layer formation on the substrate. One major advantage of PECVD over... 

Thin film deposition methods based on gas-phase processes such as CVD, evaporation, and sputtering are straightforward and thin films with good purity and structural properties can be produced. However, there are some drawbacks, such as the strict instrumentation requirement, relatively high processing cost, as well as gaseous waste treatment. In comparison, chemical and electrochemical solution methods are cost-effective and waste is confined to the solution. 

Molecular beam epitaxy (MBE) is a thin film deposition method with exceptional control over the deposit growth. It is the author s contention that there are no fundamental reasons why electrodeposition cannot achieve a similar degree of control. 

Figure 3 shows a somewhat idealized process flow. It starts with the blanket deposition of material A by virtually any thin film deposition method onto a substrate (a). The sample is then coated with photoresist, which is exposed (b) and developed (c). The photoresist masking... 

Different thin film deposition methods can be used to engineer the above-mentioned functional properties of the complex oxides, depending mainly on... 

Solution Deposition of Thin Films. Chemical methods of preparation may also be used for the fabrication of ceramic thin films (qv). MetaHo-organic precursors, notably metal alkoxides (see Alkoxides, metal) and metal carboxylates, are most frequently used for film preparation by sol-gel or metallo-organic decomposition (MOD) solution deposition processes (see Sol-GEL technology). These methods involve dissolution of the precursors in a mutual solvent control of solution characteristics such as viscosity and concentration, film deposition by spin-casting or dip-coating, and heat treatment to remove volatile organic species and induce crystaHhation of the as-deposited amorphous film into the desired stmcture. 

Hankare, P. P. Chate, P. A. Delekar, S. D. Bhuse, V. M. Asabe, M. R. Jadhav, B. V. Garadkar, K. M. 2006. Structural and opto-electrical properties of molybdenum diselenide thin films deposited by chemical bath method. / Cryst. Growth 291 40-44. 

Lindroos, S. Charreire, Y. Bonnin, D. Leskela, M. 1998. Growth and characterization of zinc sulfide thin films deposited by the successive ionic layer adsorption and reaction (SILAR) method using complexed zinc ions as the cation precursor. Mater. Res. Bull. 33 453—459. 

Pathan, H. M. Sankapal, B. R. Desai, J. D. Lokhande, C. D. 2003. Preparation and characterization of nanocrystalline CdSe thin films deposited by SILAR method. Mater. Chem. Phys. 78 11-14. 

Puiso, J. 2004. Growth kinetics and properties of lead sulfide thin films deposited on crystalline silicon using successive ionic layer adsorption and reaction method. Ph.D. thesis. Kaunas University of Technology, Kaunas, Lithuania. 

Wang, L. Kang, S. Mu, J. 2006. Electrical properties of Ag thin films deposited by the improved SILAR method./. Dispersion Sci. Technol. 27 393-397. 

K.R. Zhang, F.R. Zhu, C.H.A. Huan, and A.T.S. Wee, Effect of hydrogen partial pressure on optoelectronic properties of indium tin oxide thin films deposited by radio frequency magnetron sputtering method, J. Appl. Phys., 86 974—980, 1999. 

Evaporation is a simple and well understood vacuum technique for thin film deposition. The material to be deposited is heated until it starts to evaporate. Mainly two methods are used for evaporation ... 

In this chapter we discuss how solid surfaces can be modified. Surface modification is essential for many applications, for example, to reduce friction and wear, to make implants biocompatible, or to coat sensors [405,406], Solid surfaces can be changed by various means such as adsorption, thin film deposition, chemical reactions, or removal of material. Some of these topics have already been discussed, for example in the chapter on adsorption. Therefore, we focus on the remaining methods. Even then we can only give examples because there are so many different techniques reflecting diverse applications in different communities. 

Before we focus on chemical vapor deposition let us briefly mention other methods for thin film deposition. Films with thicknesses from 1 /zm to several 10 /zm play a fundamental role in everyday life, for example as paints and coatings. Processes during film formation are complex and a discussion would exceed the scope of this book. Introductions are Refs. [407,408],... 

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