General synthesis of homoleptic indium alkoxide complexes and the chemicalvapor deposition of indium oxide films

A general synthetic route to homoleptic indium alkoxide complexes was devel oped, and one of the new compounds was used as a precursor to transparent, conductive indium oxide films. The amide complex In[N-t-Bu(SiMe3)] reacted with t-BuOH, EtMe2COH, Et2MeCOH and i-PrMe2COH to yield the dimers [In(mu-O R)(OR)(2)](2) (R = t-Bu, CMe2Et, CMeEt2, and CMe(2)i-Pr) in high yield. Sim ilar reactions of In[N-t-Bu-(SiMe3)](3) with the less bulky alcohols i-PrOH and Et2HCOH yielded, respectively, insoluble [In(O-i-Pr)(3)](n) and the te tramer In[(mu-OCHEt2)(2)In(OCHEt2)(2)](3), which has a six-coordinate centr al indium atom surrounded by three four-coordinate indium atoms. The compou nds [In(O-i-Pr)(3)](n) and In[(mu-OCHEt2)(2)In(OCHEt2)(2)](3) were also pre pared by reacting [In(mu-O-t-Bu)(O-t-Bu)(2)](2) With an excess of the respe ctive alcohols. Attempts to prepare the previously reported oxo cluster In- 5(mu(5)-O)(mu(3)-O-i-Pr)(4)(mu(2)-O-i-Pr)(4)(O-i-Pr)(5) by thermally decomp osing [In(O-i-Pr)(3)](n), failed. The reaction between In[N-t-Bu(SiMe3)](3) and 2,6-diisopropylphenol afforded the bis tert- butylamine adduct In(O-2, 6-i-Pr2C6H3)(3)(H2N-t-Bu)(2). The evidence suggests that the tert-butylamin e ligands in In(O-2,6-i-Pr2C6H3)(3)(H2N-t-Bu)(2) resulted from a secondary reaction between HN-t-Bu(SiMe3) and 2,6-diisopropylphenol. The powerful don or p-(dimethylamino)pyridine (p-Me(2)Npy) reacted with [In(mu-O-t-Bu)(O-t-B u)(2)](2) to yield 5-cocordinate In(O-t-Bu)(3)(p-Me(2)Npy)(2) and with the more sterically encumbered complex [In(mu-OCMeEt2)(OCMeEt2)(2)](2) to yield four-coordinate In(OCMeEt2)(3)(p-Me(2)Npy). In addition, [In(mu-O-t-Bu)-(O -t-Bu)(2)](2) reacted with 2,2,6,6-tetramethyl-3,5-heptanedione (t-Bu-2-bet a-diketone) to afford (t-BuO)(2)In(mu-O-t-Bu)(2)In(t-Bu-2-beta-diketonate)( 2), which has four- and six-coordinate indium centers and virtual C-2 symme try. X-ray crystallographic studies were carried out for [In(mu-O-t-Bu)(O-t -Bu)(2)](2), In[(mu-OCHEt2)(2)In(OCHEt2)(2)](3), In(O-2,6-i-Pr2C6H3)(3)(H2N -t-Bu)(2). 1/2C(7)H(9), In(O-t-Bu)(3)(p-Me2NPY)(2). 1/2Et(2)O, In(OCMeEt2)( 3)(p-Me(2)Npy), and (t-BuO)(2)In(mu-O-t-Bu)(2)In(t-Bu-2-beta-diketonate)(2) Thet-amoxide complex [In(OCMe2Et)(3)](2) and oxygen were used as precursor s to deposit transparent, highly conductive indium oxide films on silicon, glass, and quartz substrates at substrate temperatures of 300-500 degrees C in a low-pressure chemical vapor deposition process. A backscattering spec trum indicated the film deposited at 500 degrees C was stoichiometric In2O3 (O/In = 1.46 +/- 0.07). The films were transparent in the visible region ( >75%) and had resistivities as low as 9.1 x 10(-4) Omega cm. X-ray diffraction studies indicated the films deposited on glass were cubic and highly (100) oriented.