Nano-scale depth-varying recrystallization of oblique Ar+ sputtered Si(111) layers

Abstract

Silicon, the workhorse of semiconductor industry, is being exploited for various functional applications in numerous fields of nanotechnology. In this paper, we report the fabrication of depth controllable amorphous silicon (a-Si) layers under 80 keV Ar + ion sputtering at off-normal ion incidences of 30°, 40° and 50° and crystallization of these amorphous Si(111) layers under thermal annealing. We find that the irradiated samples were not fully amorphized even for the lowest oblique incidence of 30°. Sputtering at off-normal incidences induces depth controllable surface amorphization in Si(111). Annealing at temperature of 1,073 K is characterized by formation of depth-varying buried amorphous layer due to defect recrystallization and damage recovery. Some remnant tensile stress has been observed for recrystallized samples even for lowest oblique incidence. the correlation of amorphization and stress due to sputtering induced by oblique incidence has been discussed systematically. the possible mechanism of recrystallization is discussed in terms of vacancies produced in sputtering dominated regime and their migration during annealing treatment. our results reveal that with appropriate selection of oblique ion beam sputtering parameters, depth controllable surface amorphization and recrystallization may be fine-tuned to achieve co-existing amorphous and crystalline phases, playing a crucial role in fabrication of substrates for ic industry. Silicon, the workhorse of semiconductor industry, is being exploited for the various applications in numerous fields of nanotechnology like development of FETs and infrared detectors 1-3. The combined amorphous and crystalline phases of silicon play a crucial role in the fabrication of substrates for IC industry and hence, deciding circuit performance and reliability 4-6. The process of ion implantation has become a versatile tool for producing doped regions in FETs source, channel and drain in semiconductors 1,4-8. In this regard, low energy ion irradiation is widely employed in IC industry for producing bipolar transistors in semiconductors, especially in silicon substrates. This technique offers advantage of implanting controllable quantity of incident ions into the shallow surface layers of substrate with good accuracy 5-8. In addition to these beneficial features, this non-equilibrium method disorders the equilibrium crystalline structure of the single crystal material by inducing amorphization as well as damage in the lattice 5-7,9,10. The extent and nature of these ion beam induced imperfections in the lattice limits the performance and reliability of semiconductor devices and circuits 1,6,11. This, in turn, necessitates the recovery of crystalline order of the lattice 5,9,10,12,13. It is well known that recovery from disordered surface layers is eventually a diffusive process. Hence, the well known viable tool for restoring ordered crystalline structure, recovery of ion beam induced imperfections & defects and activation of dopants is thermal annealing 4,9,10,12. Ion i...

Time-dependent surface modification of uranium oxides exposed to water plasma

“…43 Also a previous study on UO 2 film showed that its oxidation (into UO 2+x ) leads to less defined U 4f satellite intensity peaks. 45 Conversely, sample annealing, which restores the crystal order, 46 intensifies the satellite peaks. 46 In the present case by oxidation, the plasma alters the initial fluorite structured UO 2 into layer structured UO 3 .…”

“…45 Conversely, sample annealing, which restores the crystal order, 46 intensifies the satellite peaks. 46 In the present case by oxidation, the plasma alters the initial fluorite structured UO 2 into layer structured UO 3 . This process destroys crystal order.…”