Fabrication and characterization of nanomaterials grown by electron beam induced deposition process.

摘要

Platinum- and tungsten-containing materials were grown on bulk substrates from a variety of precursors including (CH3)3CH3C5H4Pt, W(CO)6, WF6, and Pt(PF3)4 in either a high vacuum dual beam focused ion beam/scanning electron microscope (FIB/SEM) or an environmental scanning electron microscope (ESEM). The effects of deposition conditions on the growth kinetics, microstructure and composition of the grown materials, structural and chemical homogeneity of impurities inside the deposits as well as the resistivity were investigated.;First, Pt-containing deposits were grown in high vacuum SEM using (CH 3)3CH3C5H4Pt. The deposits consisted of platinum nanocrystals embedded in an amorphous matrix and intermixed with the amorphous oxide on a Si substrate. The extent of intermixing scaled with the electron beam fluence delivered to the material during EBID, and during post-growth electron beam irradiation in high vacuum (in the absence of the precursor). Second, ESEM was used to perform deposition using WF6. The deposits consisted of WO3 nanocrystals embedded in an amorphous matrix. Oxide formation was attributed to residual oxidizers present in the ESEM chamber during EBID. Under conditions of fixed low electron flux, the WO3 grain size and the degree of deposit crystallinity increased with time. These changes correlated with the degree of electron energy deposition into the material during growth. Third, W-containing nanowires were grown using W(CO)6 in high vacuum SEM. With increasing electron beam energy, the resistivity increased from 2.0x107 muO cm to 1.2x109 muO cm, while the carbon sp 2/sp3 bond ratio decreased from 1 to 0.6. The increase in resistivity was attributed to the decreasing fraction of graphitic (sp 2) bonded carbon inside the deposits. Finally, Pt-containing nanowires were grown from (CH3)3CH3C5H 4Pt in high vacuum SEM and Pt(PF3)4 in ESEM. The resistivity (∼ 104 muO cm) from nanowire grown from Pt(PF3)4 was about four orders of magnitude smaller than that (∼ 108 muO cm) from those grown from (CH 3)3CH3C5H4Pt. Cross-sectional TEM analysis revealed that the nanowires formed by decomposition of Pt(PF 3)4 have a higher degree of crystallinity and a larger size grain size and higher grain packing density compared to those by (CH 3)3CH3C5H4Pt.