Mixed-Substituted Single-Source Precursors for Si_1–xGe_x Thin Film Deposition

Abstract

A series of new mixed-substituted heteronuclear precursors with preformed Si–Ge bonds has been synthesized via a two-step synthesis protocol. The molecular sources combine convenient handling with sufficient thermal lability to provide access to group IV alloys with low carbon content. Differences in the molecule–material conversion by chemical vapor deposition (CVD) techniques are described and traced back to the molecular design. This study illustrates the possibility of tailoring the physical and chemical properties of single-source precursors for their application in the CVD of Si1–x Ge x coatings. Moreover, partial crystallization of the Si1–x Ge x has been achieved by Ga metal-supported CVD growth, which demonstrated the potential of the presented precursor class for the synthesis of crystalline group IV alloys.

Dope it with germanium: selective access to functionalized Si5Ge heterocycles

“…18,29 In the present case, [SiCl 3 ] − can target either Si 2 Cl 6 or Me 2 GeCl 2 , with the attack on the dichlorogermane apparently being preferred: Analogous to the synthesis of 1 (R = Ph, n Bu; Fig. 1), 12 we converted Me 2 GeCl 2 quantitatively and instantaneously to Cl 3 Si–Me 2 Ge–SiCl 3 ( 1 , R = Me) by adding exc. Si 2 Cl 6 and cat.…”

“…15 For several years, our group has been developing the Si 2 Cl 6 /[ n Bu 4 N]Cl silylation system 16 for the synthesis of novel organosilanes 17 and oligosilanes. 18–20 Recently, we have also adapted it successfully for the preparation of mixed chlorosilane-organogermane oligomers, such as the tri- ( 1 ), 12 tetra- ( 2 ), 12 and neo -pentatetrelanes ( 3 ), 21 or the heteroadamantanes 4–6 (Fig. 1).…”

“…In stark contrast, structurally well-defined heteronuclear oligomers containing both Si and Ge atoms in their backbones have received much less attention, although the targeted doping of an oligosilane chain with more electronegative Ge atoms should provide an efficient means of tuning the oligomer's electronic structure (Allred-Rochow electronegativities: 8 Si = 1.74, Ge = 2.02). In addition, volatile Si x Ge y species are promising single-source precursors for the deposition of mixed (hexagonal) Si x Ge y alloys, [9][10][11][12] which not only have important applications in high-speed microelectronic devices, 13 but also possess potential as direct band-gap emitters, making them ''an ideal material system in which to combine electronic and optoelectronic functionalities on a single chip''. 14 Single-source Si x Ge y precursors not only allow better control over the composition of the deposited semiconductor film, but also require the adjustment of only a single kinetic parameter, i.e., the flow rate of the precursor at the specified temperature.…”

Group IV heteroadamantanes: synthesis of Si6Sn4and site-selective derivatization of Si6Ge4

“…Potential structure-determining factors are (i) the choice of substituents R and (ii) the nature of the group IV element E in the R 2 E unit. Since it is known that the reaction of R 2 GeCl 2 with Si 2 Cl 6 /Cl − (R = Ph, n Bu) furnishes chain-like oligomers Cl 3 Si–(R 2 Ge) n –SiCl 3 ( n = 1, 2) 23 instead of heteroadamantanes, we focus here on the use of Me 2 ECl 2 (E = Si, Sn): while Me 2 SiCl 2 proved inert toward Si 2 Cl 6 /Cl − , Me 2 SnCl 2 gave an inseparable 1 : 1 mixture of heteroadamantanes Sn[2] and iso-Sn[2] (Scheme 1). This result is relevant beyond the actual question of isomer distribution as it answers our third question by proving that our synthesis approach to rare mixed Si,Ge-oligomers also opens the gate to corresponding Si,Sn-compounds.…”

“…Specifically, we prepared open-chain species (Cl 3 Si) 4 Ge 21,22 or Cl 3 Si-(R 2 Ge) n -SiCl 3 (n = 1, 2; R = Ph, nBu) and applied them as precursors in the chemical vapor deposition (CVD) of Si x Ge 1Àx alloys after hydrogenation. 23 The use of Me 2 GeCl 2 gave access to (Cl 2 Si) 5 -(Me 2 Ge) monocycles 24 and even the tricyclic heteroadamantane Ge[2], which contains two SiCl 2 units together with four GeMe 2 and four Si-SiCl 3 vertices in the cluster core (Scheme 1; general formula E[X]: Si,E-adamantane with ''X'' SiCl 2 groups in the cluster core). 25 A Cl À ion-induced rearrangement reaction leads from Ge[2] to Ge[1] (one remaining SiCl 2 ), and Ge[0] (zero remaining SiCl 2 ) at room temperature and 60 1C, respectively.…”