Phase transition on the Si(001) clean surface prepared in UHV MBE chamber: A study by high resolution STM and in situ RHEED

Abstract

Pre-growth preparation of the Si(001) clean surface is a key process for Ge/Si UHV MBE. It usually includes pre-cleaning by liquid etchants, thermal pretreatment in UHV and removal of SiO2 or a different protective coat prior to MBE. Chemical pre-cleaning usually results in formation of the thin SiO2 film or the surface passivated by H. Depending on chemical pretreatment different purification processes are applied to prepare the clean surface in UHV. A structure of the Si(001) surface which may affect MBE was studied by STM and RHEED. Experiments were carried out in UHV using the Riber SSC2 instrument coupled with GPI-300 STM. Si wafers were either etched beforehand in the solutions of RCA or HF and HNO3 mixture or passivated in the HF solutions. The (2x1) reconstruction was found to mainly arise in UHV after deoxidization processes such as high-temperature annealing or SiO2 removal by a weak flux of Si. The c(8x8) structure was also often observed by STM at room temperature and found to occupy whole surface or a part of it depending on sample cooling rate and chemical pretreatment. The c(8x8) structure observed by STM was evidenced to correspond to (4x4) one in the RHEED patterns; the later replaced (2x1) when the samples were cooled below 600C and turned out to be reversible with the transition point of ~600C. A structural model of the c(8x8) surface and a pathway of its formation in assumption of surface stress field self ordering are proposed.

arXiv commentA lecture at E-MRS 2010 Fall Meeting; Nanoscale Research Letters, 2011; http://www.nanoscalereslett.com/content/6/1/218

References in corpus (6)

• Detailed analysis of scanning tunneling microscopy images of the Si(001) reconstructed surface with buckled dimers
• Nucleation of Ge quantum dots on the Si(001) surface
• CMOS compatible dense arrays of Ge quantum dots on the Si(001) surface: Hut cluster nucleation, atomic structure, and array life cycle during UHV MBE growth
• Structure and peculiarities of the (8 x n)-type Si(001) surface prepared in a molecular-beam epitaxy chamber: a scanning tunneling microscopy study
• Atomic structure of Ge quantum dots on the Si(001) surface
• Defects of Ge quantum dot arrays on the Si(001) surface

Cited by in corpus (10)

• CMOS compatible dense arrays of Ge quantum dots on the Si(001) surface: Hut cluster nucleation, atomic structure, and array life cycle during UHV MBE growth
• Ge quantum dot arrays grown by ultrahigh vacuum molecular beam epitaxy on the Si(001) surface: nucleation, morphology and CMOS compatibility
• Nucleation of Ge clusters at high temperatures on Ge/Si(001) wetting layer
• An initial phase of Ge hut array formation at low temperature on Si(001)
• Ge/Si(001) heterostructures with dense arrays of Ge quantum dots: morphology, defects, photo-emf spectra and terahertz conductivity
• Evidence for Kinetic Limitations as a Controlling Factor of Ge Pyramid Formation: a Study of Structural Features of Ge/Si(001) Wetting Layer Formed by Ge Deposition at Room Temperature Followed by Annealing at 600 °C
• Diffusion of hydrogen atoms in silicon layers deposited from molecular beams on dielectric substrates
• On atomic structure of Ge huts growing on the Ge/Si(001) wetting layer
• The formation of intermediate layers in covered Ge/Si heterostructures with low-temperature quantum dots: a study using high-resolution transmission electron microscopy and Raman spectroscopy
• Application of hydrogenation to low-temperature cleaning of the Si(001) surface in the processes of molecular-beam epitaxy: Investigation by STM, RHEED and HRTEM