FOURIER-TRANSFORM INFRARED-SPECTROSCOPY STUDIES OF HAFNIUM ALKYLBIS(PHOSPHONATE) MULTILAYERS ON GOLD - EFFECTS OF ALKYLBIS(PHOSPHONATE) CHAIN-LENGTH, SUBSTRATE ROUGHNESS, AND SURFACE FUNCTIONALIZATION ON FILM STRUCTURE AND ORDER

The influences of substrate roughness, order in the surface functional ization monolayer, and the alkylbis(phosphonate) chain length on the s tructural order of hafnium-alkylbis(phosphonate) multilayer films were investigated using external reflectance Fourier transform infrared (F TIR) spectroscopy. To examine the effects of substrate roughness, mult ilayers of hafnium-decylbis(phosphonate) (Hf-C10BP) were grown on as-e vaporated gold films and on similar films which were flame-annealed. T he influence of alkyl chain order in the surface functionalization mon olayers was investigated by preparing Hf-C10BP multilayer films on mon olayers of 4-mercaptobutylphosphonic acid (SC4P) and 12-mercaptododecy lphosphonic acid (SC12P). Effects of the bis(phosphonate) alkyl chain length on alkyl chain order in multilayer films were examined by assem bling multilayer films using hafnium and alkylbis(phosphonic acids) wi th 6-, 8-, 10-, and 12-carbon chain lengths (C(n)BPA). FTIR spectra in dicate that annealing of the gold substrate prior to functionalization and self-assembly does not significantly affect the order of the alky l chains in the multilayers. While the IR spectra of SC12P anchor mono layers indicate the alkyl chains are better ordered than monolayers of SG(4)P, the order of the alkyl chains in the Hf-C10BP multilayers gro wn on the two anchor monolayers is very similar and is less than that of the SC12P monolayer. The overall degree of alkyl chain order in the multilayers is dependent on the bis(phosphonate) chain length. Chain order decreases as the alkyl chain of the bis(phosphonate) becomes sho rter; films grown with C(5)BPA show essentially liquid-like disorder, indicating that an eight-carbon alkyl chain is the lower limit for pro ducing multilayers with some crystallinity in the alkyl chains of the organic layers.