Sputter Deposition of Transition Metal Oxides on Silicon: Evidencing the Role of Oxygen Bombardment for Fermi‐Level Pinning. Issue 23 (8th November 2019) - Poulain, Raphaël
Abstract : Different magnetron sputtering‐based deposition methods of nickel oxide SiO2 ‐passivated Si surfaces are compared. Results highlight that the presence of oxygen in the deposition chamber during reactive sputtering drastically affects the Si/SiO2 interface. An alternative method for the preparation of NiO is the sputtering of metallic nickel in oxygen‐free atmosphere followed by a post oxidation of the deposited layer in an oxygen atmosphere without plasma exposition is proposed. This method is introduced as metal layer oxidation (MLO). Using this technique, the barrier height on n‐type silicon increases from ≈0.4 eV for reactively sputtered NiO to more than 0.6 eV for the MLO method. In situ photoelectron spectroscopy evidences the formation of an extra electronic state when NiO is reactively sputtered, which is assigned to the intense oxygen ion bombardment of the Si/SiO2 surface during the process. This extra‐electronic state pins the silicon energy bands in an undesirable position. The extra‐electronic state is associated with oxygen interstitial in the SiO2 implanted during reactive sputtering. Abstract : Growth of transition metal oxides on oxidized silicon substrates opens the possibility for new device structures. Reactive sputtering of the oxide deteriorates the Si/SiO2 surface passivation. Decoupling the oxidation step from the sputter deposition of the metal can alleviate this difficulty and results in superior Si/SiO2 /TMO junctions.