S. Suh et Dm. Hoffman, General synthesis of homoleptic indium alkoxide complexes and the chemicalvapor deposition of indium oxide films, J AM CHEM S, 122(39), 2000, pp. 9396-9404
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.