Development of Novel Preparative Mass Spectrometry Instrumentation for the Advancement of New Materials and Nanofabrication.

摘要

Two instruments have been developed to soft-land species with less than 10eV. First is the laser ablation-coupled drift tube. The chamber was developed with the idea of using an inert gas, helium, to thermalize ions. This allows us to reduce the clusters KE from 40 eV to about 1 eV by producing thermal collisions between the gas and our sample. The drift chamber was assembled using a 6 four-way cross coupled with a 6 reducing cross housing the ion drift cell. Nd-YAG 532nm was utilized to ionize the sample. The clusters formed were then discriminated by cross-section and transported through the drift cell with a potential from -100 to -500 V to our mica surface. The isolated sample was then characterized using AFM and electrochemistry. The second instrument is a rectilinear ion trap with integrated ultra fast pulse valve. This instrument has some novel electronics to allow complete shut-down of the applied RF in 2 cycles. This coupled to the high pressure acquisition makes it an ideal mass filter for preparative mass spectrometry. Though the ion current is an order of magnitude less than the drift tube, the resolution is 2 orders of magnitude greater, making the two instruments complimentary. A preparative material instrument utilizing Soft Landing Ion Mobility (SLIM) to deposit and comb through the various ionized species formed using front end chemistry (figure 1.) was developed in our lab. This novel instrument has allowed us to deposit selected ions onto unmodified substrates with kinetic energies (KE) ranging from 1 eV to sub-eV. The instrument is unique in that surfaces can be created at pressures spanning from 1 100 Torr rather than usual UHV conditions. This method with low kinetic energies allows the soft-landed ions to remain intact, retaining structure for self-assembly followed by the characterization of novel materials.