Barrier Modification of Metal-contact on Silicon by Sub-2 nm Platinum Nanoparticles and Thin Dielectrics

Abstract

We report metal/p-Si contact barrier modification through the introduction of either "isolated" or "nonisolated" tilted-target-sputtered sub-2 nm platinum nanoparticles (Pt NPs) in combination with either a 0.98 nm Atomic Layer Deposited Al2O3 or a 1.6 nm chemically grown SiO2 dielectric layer, or both. Here, we study the role of these Pt's size dependent properties, i.e., the Pt NP-metal surface dipole, the Coulomb blockade and quantum confinement effect in determining the degree of Fermi level depinning observed at the studied metal/p-Si interfaces. By varying only the embedded Pt NP size and its areal density, the nature of the contact can also be modulated to be either Schottky or Ohmic upon utilizing the same gate metal. 0.74 nm Pt NPs with an areal density of 1.1 × 1013 cm-2 show ∼382 times higher current densities compared to the control sample embedded with similarly sized Pt NPs with ∼1.6 times lower areal densities. We further demonstrate that both Schottky (Ti/p-Si) and poor Ohmic (Au/p-Si) contact can be modulated into a good Ohmic contact with current density of 18.7 ± 0.6 A/cm2 and 10.4 ± 0.4 A/cm2, respectively, showing ∼18 and ∼30 times improvement. A perfect forward/reverse current ratio of 1.041 is achieved for these low doped p-Si samples.