Lewis MOCVD

Lewis, C. R., MOCVD Adds Consitency toIH-V Semiconductor Thin-layer Growth, i c5. c Z)ev., pp. 106-110 (Nov. 1985)... 

Later on, this concept was extended to precursors containing both elements of the desired material already connected by a chemical bond in a single molecule. Such precursors are mainly referred to as single source precursors. Their potential application for the deposition of thin films of the corresponding binary materials by MOCVD processes could be demonstrated. In particular Lewis acid-base adducts R3M—ER3 and four- and six-membered heterocycles [R2MER x (Fig- 1) have been in the focus of research groups both in industry and university. Consequently, the development of powerful synthetic pathways for the preparation of such precursors has been forced. 

This review has described the synthesis, structure and reactivity of important classes of group 13/15 compounds such as Lewis acid base adducts and heterocycles. In addition, their potential to serve as single source precursors for the deposition of the corresponding binary materials by MOCVD process has been demonstrated. Because of the large number of compounds containing the lighter elements of group 15, N, P and As, these... 

Superionic conducting glass systems, 12 586 Superior vena cava, 5 80 Super iron cells, 3 431t Superlattice(s), 13 499, 19 166 via MOCVD, 22 158-160 Superleaks, 17 354 Super Lewis acids, 12 191 Superluminscent LEDs, 22 176 Supermilling acid dyes, 26 396 Super milling dyes, 9 184, 185 Super-moire pattern, 17 428 Supermolecular organization, of polyamide fibers, 19 740... 

Abstract The review summarizes recent studies on the synthesis of M - Sb compounds and their potential application to serve as single-source precursor in MOCVD processes. General reaction pathways for the synthesis of simple Lewis acid-base adducts R3M - ER 3 and heterocycles of the type [R2MSbR 2]x (M = Al, Ga, In) are described. As-formed compounds were studied in detail in MOCVD processes using hot-wall and cold-wall reactors. Advantages as well as problems using single-source precursors are described. 

The main advantage of as-described heterocycUc single-source precursors compared to Lewis acid-base adducts is, that these don t tend to give MSb whiskers. Unfortunately, their volatility is much lower and the MOCVD process has to be performed under high-vacuum conditions (10 -10 mbar). In addition, the precursor has to be heated up to 130 °C in order to ensure a reasonable precursor hux rate. 

One approach to avoiding intermolecular agglomeration is the additional coordination of the alkaline earth metal ions with neutral ligands [110]. Addition of Lewis bases such as free ligand, tetrahydrofuran, ammonia, or amines to the carrier gas has afforded some improvement in vapor pressure characteristics of the most commonly used strontium and barium MOCVD precursors, Sr(dpm)2 and Ba(dpm)2 [111-119]. These effects may be due to saturation of the Lewis acidic metal centers with the gaseous bases, thereby increasing precursor vapor pressure and stability in a transient fashion. 

There has been an outburst of research interest in the structures, physical properties, and chemistry of the group 2 metal aryloxides. This is particularly true for the elements strontium and barium where work has been stimulated by the possible use of metal aryloxides as precursors (either via sol-gel or MOCVD processes) for the formation of binary and ternary oxides containing these metals.2 Synthetic procedures are based on either the halide (Be) alkyl derivatives (Mg, Grignard derivatives, etc.) or the actual metallic element (Ca, Sr, Ba). Structural studies (Tables 6.14-6.18) show for the smaller elements Be, Mg, and Ca that monomeric and dimeric structural motifs dominate, with rarer examples of trinuclear clusters, e.g. [Ca3(OPh)5(HMPA)6][OPh.2HOPh].2 2 in the case of strontium and barium a more extensive cluster chemistry has been developed for small aryloxide ligands, while monomeric units with terminal aryloxides can be formed with bulky ligands and sufficient additional Lewis bases, e.g. [Ba(OC6H2Bu2-2,6-Me-4)2(THF)3].2 ... 

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