Ultrathin silicide films were formed by starting from 1–8 nm thick Co1−xNix (x = 0, 0.25, 0.5, 0.75, and 1) at 350 °C–900 °C. For each composition x, there exists a critical thickness above which the transition temperature from monosilicides CoSi and NiSi to a disilicide-like phase increases with increasing film thickness. Below this thickness, the disilicide phase seems to form without exhibiting the monosilicides within the detection resolution limits of transmission electron microscopy and Raman spectroscopy. Raman spectroscopic analysis seems to indicate that Ni could be dissolved in the CoSi lattice to a certain fraction despite the fact that CoSi and NiSi are distinct with different crystallographic structures. Moreover, the disorder-induced Raman scattering in NiSi2 is found to be enhanced by Co incorporation. The observed annealing behaviors are attributed to variations in free energy change for phase transition caused by differences in metal thickness.

Structural and magnetic properties of quaternary Co2Mn1-xCrxSi Heusler alloy thin films

In this paper we investigate the formations and morphological stabilities of Co-silicide films using 1-8-nm thick Co layers sputter-deposited on silicon (100) substrates. These ultrathin Co-silicide films are formed via solid-state reaction of the deposited Co films with Si substrate at annealing temperatures from 450 °C to 850 °C. For a Co layer with a thickness no larger than 1 nm, epitaxially aligned CoSi2 films readily grow on silicon (100) substrate and exhibit good morphological stabilities up to 600 °C. For a Co layer thicker than 1 nm, polycrystalline CoSi and CoSi2 films are observed. The critical thickness below which epitaxially aligned CoSi2 film prevails is smaller than the reported critical thickness of the Ni layer for epitaxial alignment of NiSi2 on silicon (100) substrate. The larger lattice mismatch between the CoSi2 film and the silicon substrate is the root cause for the smaller critical thickness of the Co layer.

In this paper, junctionless MOSFETs with un-uniformly doped source/drain and channel regions have been thoroughly investigated. Un-uniformly doped junctionless MOSFET has the same type of dopants in source/drain and channel while the doping level in the source/drain is much higher than that in the channel. Performance of DC, AC and variability of the uniformly doped, un-uniformly doped junctionless and conventional P-N junction MOSFETs featuring a gate length of 16 nm has been obtained by device simulation through Silvaco software package. Compared with uniformly doped junctionless MOSFETs, un-uniformly doped junctionless MOSFETs exhibit significantly improved overall DC and AC performance as well as lower sensitivity to variations of channel thickness. In addition, un-uniformly doped junctionless MOSFETs also demonstrate marginal performance enhancement compared with conventional P-N junction MOSFETs.