Joint functioning of a magnetron sputtering system and an end-hall ion source

The features of joint operation of a magnetron sputtering system (MSS) and an end-Hall ion source (EHIS) are investigated. It is noted that the initiation of the magnetron discharge leads to partial or complete neutralization of the ion beam generated by the EHIS; in other words, in some regimes of the MSS, the ion source operates in the filament-free regime. In such a case, the magnetron discharge is the source of electrons required for sustaining the discharge and for compensating the ion beam from the EHIS. The dependences of the discharge characteristics of the EHIS and MSS are established when a filament neutralizer and MSS discharge are used for compensating the EHIS ion beam. The balance of currents in the ion source-magnetron sputtering system is considered by analyzing the joint functioning of the MSS and EHIS. It is shown that the maximal discharge current from the ion source for which the charge compensation condition is preserved depends on the unbalance and the magnetron discharge current.     

Network single-walled carbon nanotube-field effect transistors (SWNT-FETs) with increased Schottky contact area for highly sensitive biosensor applications

Highly sensitive single-walled carbon nanotube-field effect transistor (SWNT-FET) devices, which detect protein adsorptions and specific protein-protein interactions at 1 pM concentrations, have been achieved. The detection limit has been improved 104-fold compared to the devices fabricated by photolithography. The substantially increased sensitivity is mainly due to the increased Schottky contact area which accommodates relatively more numbers of proteins even at very low concentration. The augmented number of proteins adsorbed on a device induces instant modulation of the work function of metal contact electrodes, which eventually changes the conductance of the device. Such devices have been attained by addressing metal electrodes on network-type SWNTs using a shadow mask on a tilted angle sample stage. The shadow mask allows metals to penetrate underneath the mask efficiently, therefore forming a thin and wide Schottky contact area on SWNT channels.