Alternating silicon oxy-nitride and silicon oxide stripe formation by nitric oxide (NO+) ion implantation

Abstract

We report nitric oxide ion (NO+) beam induced nanoscale pattern formation on Si (100) surface. The patterns are found to be structurally as well as chemically periodic. A highly reactive 14 keV NO+ beam is developed in an Electron Cyclotron Resonance ion beam system and implanted on Si (100) surface at oblique angles to form a periodic nano-ripple pattern with specific silicon oxide and silicon oxy-nitride enriched sectors with different dielectric constants. Well-defined ripple patterns start to form at comparatively lower ion fluences due to an additional instability generation by the chemical reaction of NO+ ions with silicon. The chemical shift of the Si 2p peak in the x-ray photoelectron spectroscopy study of an ion irradiated sample confirms the formation of silicon oxide and silicon oxy-nitride, whereas the local chemical nature of the ion induced ripple patterns, probed by electron energy loss spectroscopy, approves spatially resolved silicon oxide and silicon oxy-nitride stripe pattern formation. The ion modified layer thickness measured by cross-sectional transmission electron microscopy has an excellent agreement with Monte Carlo simulations. The optical sensitivity of an NO+ bombarded chemically patterned Si surface is also studied by UV–Visible spectroscopy. Formation mechanisms and potential applications of such nano-scale spatially graded materials are discussed.

Spatially varying chemical phase formation on silicon nano ripple by low energy mixed ions bombardment

“…The carbon in virgin Si arises during the industrial processing of silicon wafer, whereas the presence of oxygen is due to the native silicon oxide layer on Si. The presence of native oxide and C in both virgin and ion bombarded Si surfaces was also observed earlier [13,16]. A change in the intensity level of the above elements as well as the presence of nitrogen (N) in mixed ion (N 2 + and CO + ) bombarded sample, is detected in the spectrum.…”

“…The high-resolution Si 2p peak of virgin Si in figure 4(a) is best fitted by two Gaussian-Lorentzian (GL-30) peaks positioned at 99.4 eV (FWHM 1.02 eV) and 103.5 eV (FWHM 1.8 eV) corresponding to elemental Si and the native silicon oxide [39], respectively. The high-resolution Si 2p spectrum for mixed ion bombarded Si (figure 4(b)) is best fitted by five Gaussian-Lorentzian peaks, positioned at 99.5 eV (FWHM 0.82 eV), 100.1 eV (FWHM 1.16 eV), 101.3 eV (FWHM 1.83 eV), 102.7 eV (FWHM 2 eV) and 103.2 eV (FWHM 1.9 eV), indicating the presence of non-reacted elemental Si, silicon carbide [40,41], silicon nitride (Si 3 N 4 ) [42], silicon oxynitride (Si 2 N 2 O) [43], and silicon oxide (SiO 2 ) [16,39], respectively. In order to ensure the formation of the above chemical compounds, the high-resolution spectra of carbon, nitrogen and oxygen are also recorded.…”

“…co-deposition of metal impurities during inert ion bombardment [12] and impure ion bombardment [13]. Bombardment of the solid target with a single or two reactive ion species is also studied [14][15][16]. However, the growth of surface patterns and chemical phases by simultaneous irradiation of multiple reactive ions is interesting and challenging.…”

Surface nanopatterning by ion beam irradiation: compositional effects

“…At this stage, the NO + ion beam impinges mainly on the upwind sides facing the incoming beam, which become silicon oxy-nitride-rich, while the downwind sides are shadowed from the incoming ion beam and remain silicon oxide-rich. These chemical and morphological patterns develop as a consequence of the interplay of the dissimilar chemical reactivity of oxygen and nitrogen with silicon, slope-dependent ion implantation, unequal SR of elemental silicon, silicon oxide, oxy-nitride and nitride, and the beam shadowing effect [236]. These concepts were further employed for irradiating a Si surface with a mixed (CO + and N + 2 ) ion beam at θ = 60 • .…”

Ion Beam Nanopatterning of Biomaterial Surfaces

“…This is particularly obvious when reactive ions such as O 2 + or N 2 + are used, which may react with the atoms of the target surface and, thus, form thin oxide and nitride films, respectively. Due to the developing surface topography, these films may display pronounced local variations in thickness and stoichiometry and, thereby, have dramatic effects on the evolution of the nanopatterns, while the fabricated surface may exhibit a highly heterogeneous stoichiometry [95,96]. However, even when inert ions such as noble gas ions are employed, changes in surface chemistry may occur.…”