Sharon L. Blair

Solid state photochemistry of (C2H4(Ph2P)2)M(N3)2 (MNi, Pd, Pt) on Si(111) surfaces

Abstract The photochemistry of (C 2 H 4 (Ph 2 P) 2 )M(N 3 ) 2 (MNi, Pd, Pt) has been investigated under a variety of conditions. In a styrene oxide glass, at 77 K, photolysis leads to loss of all azides (MNi, Pt) and presumably the production of (C 2 H 4 (Ph 2 P) 2 )M. For MPd a single intermediate containing an azide, (C 2 H 4 (Ph 2 P) 2 )Pd(N 3 ), is observed. When the complexes are deposited on a silicon surface and photolysed at room temperature loss of a single azide and production of (C 2 H 4 (Ph 2 P) 2 )M(N 3 ) are observed. This intermediate is photosensitive and prolonged photolysis yields loss of all azide from the molecules. The final film, examined by Auger spectroscopy, indicates that further reaction is dependent on the metal. In the case of nickel all ligands are lost and metallic nickel is formed. For platinum the final product retains some dppe to give a stoichiometry of Pt(dppe) 0.1 . The final product in the case of palladium has an approximate stoichiometry of Pd(dppe) 0.85 . Photolysis of any of these materials in powder form results in a much less efficient photoreaction with no evident intermediate.

Molecular design for photo and electron beam lithography with thin films of coordination compounds

Abstract The photochemistry of coordination complexes in the solid state has been investigated with a view towards developing a new method for the photolithographic deposition of materials. Ultraviolet exposure of thin films of coordination complexes through an optical lithography mask results in the patterning of materials in the exposed regions. The development of this method requires photochemically active complexes which efficiently eject ligands upon photolysis to produce the desired material in a solid state thin film. A generic reaction for the production of metal films is M L n ( thin film ) → h v M ( thin film ) + n L ( g ) In this paper the photochemistry of thin films of inorganic complexes of Co, Cu, Ni, Pd, Pt and U is presented. These examples will be used to outline the approaches used to design suitable precursor molecules for film deposition. Mechanistic studies of the surface photochemical reactions along with evidence for submicron resolution lithography of materials derived from these complexes will be highlighted. The use of electron beams to induce similar chemistry will also be discussed.

Solid-state photochemistry of platinum(II) methylazide complexes as thin films on Si (111) surfaces: photolithography of platinum films

The solid-state photochemistry of L2Pt(Me)(N3) (L=PPh3, PEt3, dppe/2) have been investigated on Si (111) surfaces. Photolysis of an amorphous thin film of L2Pt(Me)(N3) results in the loss of all ligands. This occurs via a single photon process with no detectable thermally stable intermediate. The resultant films are primarily platinum metal although some phosphine-containing impurity remains. The final analysis leads to formulations of the films as Pt(dppe)0.06, Pt(PPh3)0.12 and Pt(PEt3)0.07. The thicknesses of the platinum films ranged from 150 nm to less than 25 nm. This process was shown to be compatible with standard lithography methods by the production of 3 μm wires on Si (111) by photolithography.

Use of complex coordination chemistry for the deposition of inorganic materials: spin on metals and photoresist-free lithography

The chemistry of coordination complexes in the solid state has been investigated with a view towards developing new methods and processes for the deposition of materials. The processes investigated include the development of spin on metals and photolithographic deposition methods. In the spin on metal process a film of an appropriate complex is spin cast and thermalized to deposit the requisite metal. For photolithographic deposition a precursor film is deposited. Ultraviolet exposure of the films through an optical/UV lithography mask results in the patterning of materials in the exposed regions. The development of this method requires photochemically active complexes which efficiently eject ligands upon photolysis to produce the desired material in a solid state thin film. A generic reaction for the production of metal films is illustrated in equation 1. MLn(thin film) (Delta )hvyields M(thin film)+ n L(g). In this paper the thermal, photo and electron beam induced chemistry of thin films of inorganic complexes of lead and chromium is presented.

The photochemical production of nickel films from thin films of the inorganic nickel complexes trans-NiN4X2 (N2Et2NC2H4NH2, MeHNC2H4NMeH; XNO2, NO3, NCS)

Abstract The solid state photochemistry of trans -NiN 4 X 2 (N 2 Et 2 NC 2 H 4 NH 2 , MeHNC 2 H 4 NMeH; XNO 2 , NO 3 , was studied. All these molecules undergo photoinduced loss of X or X − as the primary photoprocess. The complexes trans -Ni(MeHNC 2 H 4 NMeH) 2 (X) 2 (XNCS, NO 3 ) undergo loss of X as an anion to yield thermally stable ion pairs of the type [Ni(MeHNC 2 H 4 NMeH) 2 X][X]. These ionic products are photosensitive, decaying with loss of all ligands to form metal films. The remaining complexes trans -NiN 4 X 2 (N 2 Et 2 NC 2 H 4 NH 2 , X NO NO 3 , NCS, N 2 MeHNC 2 H 4 NMeH; XNo 2 ) undergo photoextrusion of X as a radical. This primary photoprocess does not yield stable intermediates and the resultant Ni(I) complexes decompose in a rapid thermal reaction These results are interpreted in terms of charge transfer reactivity which results in radical loss, or ligand field reactivity which results in loss of the ion. Either type of reactivity results in the loss of all ligands and the formation of metal films.

Photochemistry of thin amorphous films of Fe(CO)4PPh3 on Si(111) surfaces

Abstract The photochemical reactions of Fe(CO) 4 PPh 3 and Fe(CO) 3 (PPh 3 ) 2 as amorphous films on silicon surfaces are presented. The mechanism of the reaction of Fe(CO) 4 PPh 3 in the films has been studied in some detail. Initial CO loss leads to a thermally unstable intermediate, Fe(CO) 3 PPh 3 , which decomposes in the film leading to the production of iron. In thick films photoproduced CO remains trapped in the film and may react with Fe(CO) 3 PPh 3 , regenerating the starting material. Further evidence for this intermediate arises from experiments conducted with PPh 3 added to the film. In these films the initial photoproduct is trapped by PPh 3 yielding Fe(CO) 3 (PPh 3 ) 2 . A quantitative study of the quantum yield efficiency in these films was undertaken. The Fe(CO) 3 (PPh 3 ) 2 films are photosensitive undergoing CO loss to yield Fe(CO) 2 (PPh 3 ) 2 , as demonstrated by its trapping, by PPh 3 , to form Fe(CO) 2 (PPh 3 ) 3 . Extended photolysis of Fe(CO) 3 (PPh 3 ) 2 films, including those containing photoproduced Fe(CO) 2 (PPh 3 ) 3 , results in the formation of iron. The surface photochemistry of both Fe(CO) 4 PPh 3 , and Fe(CO) 3 (PPh 3 ) 2 are shown to be compatible with standard lithography. Patterns of 1×100 μ m lines of iron oxide were easily produced on a silicon surface.

Photochemistry of bistriphenyl phosphine nickel dicarbonyl on silicon surfaces: the lithographic deposition of nickel and nickel-iron, nickel-chromium and iron-chromium containing films

The photolysis of Ni(CO)2(PPh3)2 as surface films on silicon surfaces has been investigated. The photolysis of the title complex leads to the loss of ligand from the coordination sphere and the formation of nickel. The ligands are largely lost to the gas phase although impurity originating from the triphenylphosphine ligand remains within the film. The controlled construction of films formed from a mixture of Ni(CO)2(PPh3)2 and Cr(CO)5PPh3 could be accomplished by spin coating from a solution containing both precursors. Photolysis of films composed of a mixture of Ni(CO)2(PPh3)2 and Cr(CO)5PPh3 resulted in the formation of a nickel-chromium film. In a similar fashion films constructed from of Ni(CO)2(PPh3)2 and Fe(CO)4PPh3 could be photolysed to generate films of nickel-iron and films composed of Cr(CO)5PPh3 and Fe(CO)4PPh3 could be photolysed to generate films of chromium-iron. Both of these films contained impurities associated with remnant triphenylphosphine and oxidation of the surface. This process was shown to be compatible with standard lithography techniques by the lithography of 2 μm lines of triphenylphosphine contaminated nickel on a silicon surface.