Mechanism of cleaning Si(100) surface using Sr or SrO for the growth of crystalline SrTiO3 films

Abstract

A method for removing SiO2 and producing an ordered Si(100) surface using Sr or SrO has been developed. In this technique, a few monolayers of Sr or SrO are deposited onto the as-received Si(100) wafer in an ultrahigh vacuum molecular-beam epitaxy system. The substrate is then heated to ∼800 °C for about 5 min, the SiO2 is removed to leave behind a Sr- or SrO-terminated ordered Si(100) surface. This Sr- or SrO-terminated Si(100) surface is well suited for the growth of crystalline high-k dielectric SrTiO3 films. Temperature programmed desorption measurements were carried out to understand the mechanism of removing SiO2 from Si(100) using Sr or SrO. The species we observed coming off the surface during the temperature cycle were mainly SiO and O, no significant amount of Sr containing species was observed. We conclude that the SiO2 removal is due to the catalytic reaction SiO2+Sr(or SrO)→SiO(g)+O+Sr(or SrO). The reaction SiO2+Si→2SiO(g) at the SiO2/Si interface is limited and the pit formation is suppressed. The main roles that Sr or SrO play during the oxide removal process are catalysts promoting SiO formation and passivating the newly exposed Si surface, preventing further etching and the formation of pits in the substrate.

Epitaxial growth of topological insulator Bi2Se3 film on Si(111) with atomically sharp interface

“…Since the beginning of Si MBE growth, most common method employed to clean the Si substrate has been a multicycle high-temperature flashing process or annealing up to ~1200 o C [32,[34][35][36]; and all previous reports to grow thin films on Si used such high temperature cleaning methods [10,37].…”

Interfacial reaction in the growth of epitaxial SrTiO3 thin films on (001) Si substrates

“…In sample A, the native SiO 2 on the silicon surface was removed by a strontium "deoxidation" process, which is explained in Ref. 35. In samples B and C, the native oxide was removed by heating to ϳ900°C in vacuum.…”

“…A SiO 2 -free silicon surface, identified by a sharp double-domain 2 ϫ 1 Si͑001͒ RHEED pattern, was obtained either through a strontium deoxidation process 35 or heating in ultrahigh vacuum ͑UHV͒ to ϳ900°C. Upon the clean ͑001͒ Si surface at a substrate temperature of 700°C ͑measured by an optical pyrometer͒, a strontium dose of 3.4ϫ 10 14 at./ cm 2 ͓one-half a monolayer 36 ͑ML͒ of strontium͔ was deposited from a strontium MBE source at a flux of ͑3-4͒ ϫ 10 13 at./ cm 2 / s. This formed an interfacial strontium silicide layer 2,5,6 that functions to protect the underlying silicon from oxidation and thus preserve an epitaxial template for epitaxial-oxide overgrowth.…”

Molecular beam epitaxy growth of SrO buffer layers on graphite and graphene for the integration of complex oxides

“…This approach was highly successful for integration of complex oxides onto silicon. For example, high-κ dielectric SrTiO 3 was first grown on Si(001) using a Sr flux to desorb SiO 2 from the surface [16], followed by silicide formation with Sr to facilitate the growth of SrO and, subsequently, SrTiO 3 [17][18][19][20][21]. These techniques produce SrTiO 3 -based metal-oxidesemiconductor field effect transistors (MOSFET) with gate leakage two orders of magnitude smaller than similar devices using SiO 2 [22].…”