Deposition of MSe (M = Cd, Zn) Filmsby LP-MOCVD from Novel Single-Source Precursors M[(SePPh2)2N]2

Abstract

In recent years, there has been a rapid development in the field of II±VI semiconductors for use in photovoltaic devices due to their intermediate energy bandgaps. [1] ZnSe and ZnS are promising materials for blue/blue±green laser diode devices [2±4] which could lead to high-density optical storage systems, as well as fast switching devices. [5±7] Cadmium chalcogenides have applications in solid state solar cells [8,9] and photoconductors, in field effect transistors, sensors, and transducers. [10] Considerable efforts have been made to develop singlesource precursors for the deposition of semiconductor compounds. There are many reports in the literature of attempts to develop effective single-source precursors for the deposition of such materials by metal±organic (MO)CVD. [1,11±15] Over the years, we have been particularly interested in the deposition of thin films of chalcogenide from diseleno-or dithio-carbamato complexes of cadmium and zinc. [16] Introduction of asymmetrical bulky substituents to the selenium ligand was particularly successful, and metal selenide (CdSe, ZnSe) films were deposited. Gas chromatography (GC) and mass spectrometry (MS) experiments, using pyrolysis, have shown that the use of methyl(n-hexyl) derivative instead of symmetric alkyl hinders the formation of diethyldiselenide and therefore inhibits the deposition of selenium during growth. [16] Another class of metal±organic compounds for metal selenide films, based on bis(diphenylphosphino)amines, e.g., [Ph 2 (Se)NHP(Se)Ph 2 ], which can coordinate with numerous metals, has now been developed. [17] Schmidpeter and Groeger first synthesized imidodiphosphinates [NH(SPPh 2 ) 2 ], [18] then later the seleno analogue was prepared by oxidation of Ph 2 PNHPPh 2 with potassium selenocyanate, followed by acidic work up, [19] or by direct reaction with selenium under reflux in toluene. [20] Thin films of CdSe and ZnSe have been grown by low pressure (LP)-MOCVD using M[(SePPh 2 ) 2 N] 2 (M = Zn or Cd), air stable single-source precursors. The precursors were prepared as described in an earlier paper. [21] In the single crystal structure of Cd[(SePPh 2 ) 2 N] 2 , the metal center is coordinated to the selenium atoms by two bidentate ligands, forming six-membered chelate rings, and the ligands display a symmetric coordination to the cadmium(II). [21] Thermogravimetric analysis (TGA) of cadmium and zinc showed that the precursors are reasonably volatile and begin to evaporate at 375 C.Metal selenide films were deposited at various growth temperatures (475, 500, and 525 C) maintaining the precursor temperature at 375 C. Little or no growth was observed at 475 C, but as growth temperature was increased, deposition of films occurred. Zinc selenide films produced at 525 C were dark orange in color, transparent, and welladherent to the glass surface (scotch tape test), however, they could be removed with a scalpel, CdSe films grown at 525 C were black in color and fairly adherent to the surface, whilst at 500 C, non-uniform gray films were deposited, ...

Experimental and Theoretical Investigations of the Contact Ion Pairs Formed by Reactions of the Anions [(EPR2)2N]− (R = iPr, tBu; E = S, Se) with the Cations [(TePR2)2N]+ (R = iPr, tBu)

“…The primary focus has been the coordination chemistry of these bidentate ligands, and several reviews that provide details of the complexes of 1 with a diverse array of main group, lanthanide and transition metals have been published. [3][4][5] A significant recent application of these complexes, particularly in the case of the selenium derivative (1, E = Se, R = i Pr), has been as single-source precursors for the generation of metal selenides in the form of semiconducting thin films [6][7][8][9][10][11][12][13][14][15][16][17] or quantum dots 18 via CVD or solvothermal processes.…”

Aerosol-assisted CVD of cadmium diselenoimidodiphosphinate and formation of a new iPr2N2P3+ ion supported by combined DFT and mass spectrometric studies

“…In addition, we have used Py-GC/MS and DFT to explain the observed trends. Under low-pressure (LP) CVD studies, the same complex exclusively deposited cadmium selenide thin films at all deposition parameters 8,28,29 . It is worth recalling that the precursor purity is essential to avoid incorporation of extraneous elements, especially those that are electrically active.…”

Experimental and Theoretical Investigations of the Redox Behavior of the Heterodichalcogenido Ligands [(EPiPr2)(TePiPr2)N]−(E = S, Se): Cyclic Cations and Acyclic Dichalcogenide Dimers

“…to be suitable single-source precursors for the generation of semiconducting thin films [5][6][7][8][9][10][11][12] or quantum dots 13 of metal selenides via chemical vapor deposition processes. After a brief hiatus, interest in this class of ligand was reinvigorated by the discovery of the first tellurium-containing examples, which were obtained as alkali metal salts (1, E = Te; R = Ph, 14 i Pr 15 ).…”