John R. Walsh

Synthesis, characterization and x-ray crystal structures of asymmetric bis(dialkyldithiocarbamates) of zinc: Potential precursors for ZnS deposition

Four new bis(dialkyldithiocarbamates) of zinc, [Zn(S2CNMeR)2]2 (where R = Et, Prn, Pri and Bun: compounds 1, 2, 3 and 4 have been synthesized and characterized by X-ray crystallography, spectroscopic methods and differential scanning calorimetry X-ray crystallographic characterization indicated centrosymmetric dimeric structures for 1–4. The central region of each molecule, consisting of three edge-sharing four-membered rings, is structurally similar to the symmetric bis(dialkyldithiocarbamates) [Zn(S2CNEt2)2]2 and [Zn(S2CNPr2i)2]2, characterized in earlier studies. Preliminary results on chemical vapour deposition of polycrystalline ZnS films from 4, which is considerably more volatile than the previously used precursor [Zn(S2CNEt2)2]2, are reported.

MOCVD Layer growth of ZnSe and ZnS / ZnSe multiple layers using nitrogen containing adducts of dimethylzinc

Abstract It is shown that adducts between dimethylzinc and the nitrogen donor ligands triethylamine and triazine can be used successfully as the zinc sources to grow ZnSe and related compounds by MOCVD. High quality single crystal layers of ZnSe have been grown without any significant pre-reaction of the constituent reactants. The high quality character of the layers is demonstrated by the presence of free exciton dominated photoluminescence. Some general points concerning the use of zinc adducts are also reviewed and discussed. In particular, it is shown that one reason for the improved purity of layers grown using adducts compared to dimethylzinc alone is the removal of iodine, an n-type donor in ZnSe, by the adducting process. The relationship between the nature of the adducting species and the control of prereaction is also discussed briefly.

Structural studies of some Group 12 metal alkyl adducts: the X-ray crystal structures of Me2Zn[Me2N(CH2)2NMe 2], Me2Cd[Me2N(CH2)2NMe2], (Me3CCH2)2Zn[Me2N(CH2)2NMe2] and (Me3CCH2)2Cd[Me2N(CH2)2NMe2]

Abstract The X-ray crystal structures of a series of group 12 metal alkyl adducts Me 2 M[Me 2 N(CH 2 ) 2 NMe 2 ] {M  Zn ( 1 ), Cd ( 2 )} and (Me 3 CCH 2 ) 2 M[Me 2 N(CH 2 ) 2 NMe 2 ] {M  Zn ( 3 ), Cd ( 4 )} have been determined. Each adduct exists as a mononuclear, molecular unit with pseudo-tetrahedral coordination at the metal centre. Compound 1 crystallizes in space group P 2 1 / a , a 13.868(3), b = 11.616(2) and c = 7.588(2) A, β = 94.83(2)°, compound 2 in space group Cmca , a = 11.196(2), b = 12.179(2) and c 17.969(3) A. Compounds 3 and 4 are isostructural in space group C 2 / c with the following unit cell dimensions for Zn {Cd}: a = 17.167(5) {17.604(5)}, b = 9.369(3) {9.484(3)}, and c = 12.916(3) {12.758(3)} A, β = 107.83(2) {106.07(2)}.° Compound 1 and the parent alkyl of 4 have been used successfully in the growth of thin films by metalloorganic chemical vapour deposition, 1 as a dopant in the growth of p-type GaAs, and [Me 3 CCH 2 ] 2 Cd as a Group 12 source in the growth of CdS.

The growth of CdS and CdSe alloys by MOCVD using a new dimethylcadmium adduct

Abstract High quality epitaxial layers of CdS and CdSe have been grown by MOCVD using a tetrahydrothiophene adduct of dimethylcadmium. Good quality layers were grown in the temperature range 300 to 500°C. Layers were grown on both (100) GaAs and (111) GaAs substrate orientation with the latter displaying the best optical properties.

The preparation, reactivity, and crystal structure of a 1 : 1 adduct of dimethylzinc and (−)-sparteine

Abstract A 1 : 1 adduct of dimethylzinc and (−)-sparteine has been prepared and characterized crystallographically; the complex is remarkably resistant to reaction with the atmosphere. The adduct is mononuclear with pseudo-tetrahedral coordination at the zinc atom. It reacts with benzoyl chloride to give acetophenone and with benzaldehyde to give ( R )-1-phenylethanol with a 15% enantiomeric excess.

The use of dimethylzinc-amine adducts for the p-doping of InP and related alloys

The adducts between dimethylzinc and the nitrogen donors triethylamine, tetramethylmethylene diamine, and triethyltriazine have been used as p-dopant sources in the growth of InP and InGaAs by metalorganic vapour phase epitaxy (MOVPE). The liquid adducts demonstrated reproducible doping over the range 5 × 1015 to 1018 cm−3 with the precise doping range being variable, depending on the adduct vapour pressure. The p-doped InP and InGaAs layers had excellent surface morphology and no detrimental gas phase reactions were observed during layer growth.

The preparation and characterization of bis(2,2-dimethylpropyl)cadmium(II) and its 2,2′-bipyridyl adduct

Abstract The synthesis and characterization of the compound bis(2,2-dimethylpropyl)cadmium(II), {bis(neopentyl)cadmium(II)} and its 1:1 adduct with 2,2′-bipyridyl are reported. The alkyl is moderately volatile (vapour pressure ca 3 torr, 52°C) and may find application as a precursor for the deposition of cadmium-containing films by MOCVD.