LITHIUM TRIALKYLSILYLAMIDES
Liquid trialkylsilylamide derivatives of lithium and other alkali metals were prepared by R. Gordon.[[i]] They have advantages in terms of evaporation rate, possibility to use for liquid delivery systems, etc.
[i]R. Gordon, R.N.R. Broomhall-Dillard, US Patent 6994800, 2006.
Lithium bis(trimethylsilyl)amide [Li(NSiMe3)2]2
Lithium bis(trimethylsilyl)amide LiN[Si(CH3)3]2 was synthesized and characterized, including concentration and temperature dependent 1H and 7Li NMR spectra in ethers and hydrocarbon solvents. The measurements results were interpreted for the presence of a monomer-dimer equilibrium in THF and a dimer-tetramer equilibrium in hydrocarbon solvents. Thermodynamic parameters for the dimer ⇄ 2 monomer equilibrium in THF solutions indicate that the monomer is preferentially solvated in solution (ΔH0 = −4.0 kcal/mole, ΔS0 = −17 cal · deg−1 · mole−1). Isopiestic molecular weight determinations were supporting these conclusions.[[i]]
Lithium bis(trimethylsilyl)amide LiN[Si(CH3)3]2 is potentially applicable as precursor.
[i] Bert Y. Kimura, Theodore L. Brown, J. Organomet. Chem., 1971, Vol.26, Iss. 1, p. 57–67, http://www.sciencedirect.com/science/article/pii/S0022328X0080594X , « Solvent effects on the aggregation of lithium bis(trimethylsilyl)amide »
[LiN(SiMe3)2]2 for LiNbO3 by ALD
Lithium trimethylsilylamide [LiN(SiMe3)2]2 (or lithium hexamethyldisilazane LiHMDS] was applied as Li
precursor for the deposition of LiNbO3 thin films on soda lime glass and Si(100) by ALD (in ASM F-120 Sat ALD reactor) (in combination with niobium ethoxide [Nb(OEt)5] and deionized water H2O as Nb and O sources). [LiN(SiMe3)2]2 was sublimed in an open boat
at 75 °C (whereas Nb(OEt)5 precursor was evaporated at 100 °C.), at substrate temperature of 235 °C, N2 was used as carrier gas (500 ml/min). Mainly soda lime
glass and Si(100) were used as substrates, however, several growths were done on Al2O3(001), Al2O3(012), SrTiO3(100) and LaAlO3(012). The deposited LiNbO3 layers were analysed by XRD, XRR, spectroscopic ellipsometry, TOF-ERDA, SEM, AFM, piezoresponse force microscopy (PFM). Film crystalline orientations were substrate-dependent: layers were polycrystalline
on Si (100), but epitaxially oriented on LaAlO3 (012), Al2O3 (012), Al2O3 (001). Good control of cation stoichiometry in LiNbO3 with low Si impurity levels were achieved, layers were shown to be ferroelectric: the coercive field of layers on Si (100) was ∼220 kV/cm, remanent polarization ∼0.4 μC/cm2. [i]
[i] E. Østreng, H.H. Sønsteby, T. Sajavaara, O. Nilsen, H. Fjellvåg, J. Mater. Chem. C, 2013, 1, 4283-4290, DOI: 10.1039/C3TC30271G , « Atomic layer deposition of ferroelectric LiNbO3 »
Lithium bis(ethyldimethylsilyl)amide [Li(NSiMe2Et)2]2
Lithium bis(ethyldimethylsilyl)amide [Li(NSiMe2Et)2]2 is liquid despite it dimeric structure (Figure 1). [Li(NSiMe2Et)2]2 is the first known distillable liquid (at RT) lithium precursor. It has viscosity 37 centipoise at 40°C.
[Li(NSiMe2Et)2]2 for LiOH, LiNbO3 by CVD
[i] R. Gordon, Electrochem Soc. Proc Vol 2000-13, p.248,
[ii] R.N.R. Broomhall-Gillard, R.G. Gordon, V.A.Wagner, Mat. Res. SocSympProc, 2000, in press.
[iii]http://books.google.de/books?hl=de&lr=&id=0-dyAtwmREsC&oi=fnd&pg=PA248&dq= gallium+thd+CVD&ots=6H2vhnImH3&sig=Ev_WwLoMw4Qq1_JMhBcIMmsK9b4#v=onepage&q&f=false
[Li(NSiMe2Et)2]2 for Li phosphate CVD
Liquid lithium bis(ethyldimethylsilyl)amide (with diisopropylphosphate as phosphate source) has been used for aerosol CVD of lithium phosphate on silicon substrates XPS showed films to contain lithium, phosphorus and oxygen. [45]
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