Transport Mechanism of Si Nanowires Contacted to Pt Deposited by Focus-Ion-Beam
Date Issued
2009
Date
2009
Author(s)
Kei, Tz-Chen
Abstract
In this thesis, The galvanic wet etching was adopted to fabricate single-crystalline n-Si nanowires (NWs) at room temperature in HF/AgNO3 solution. The focus-ion-beam-deposited Pt (FIB-Pt) was employed to connect photolithographically prepared Cr/Au (5/60 nm) pads on a Si substrate which was capped with a 600 nm thick SiO2 layer deposited by plasma-enhanced chemical vapor deposition (PECVD).First, we investigate the electrical characteristic of FIB-Pt contact to Si NWs under various Ga+ dosage. We show that FIB-Pt contact to Si NWs forms very low contact resistance compared with present studies, the specific contact resistivity was estimated in the order of 10-6 Ω-cm2. To gain insight on ultra low contact resistance, the morphologic of structure and electrical transport have been studied. The image of TEM demonstrates that the existence of FIB-induced amorphization under Pt contacts, the ultra low effective barrier height was calculated using diffusion theory. The free carrier concentration and mobility has also been estimated. Due to the existence of FIB-induced amorphization, the Fermi level pinning by surface states might be responsible for the barrier height lowering and further lower the specific contact resistivity.Second, we study the transport mechanism of Ga+ doped and undoped of n-Si NWs. The temperature-dependent four-probe measurements indicate that the electrical conductivity of the Si NWs exhibits two regimes. Thermal activated transport dominates at low temperature range. The Mott’s variable range hopping (Mott-VRH) model is applied to the conduction at high temperature range due to FIB-induced disorder. Mott’s parameters of Si NWs, such as hopping energy, hopping distance and density of states at Fermi level have been estimated.
Subjects
n-type Si
nanowire
FIB
diffusion theory
variable range hopping
Type
thesis
File(s)![Thumbnail Image]()
Loading...
Name
ntu-98-R96941100-1.pdf
Size
23.32 KB
Format
Adobe PDF
Checksum
(MD5):71968d4c46c15d99493b8c85c905e230