Roughening instability and evolution of the Ge(001) surface during ion sputtering

Chason, E.; Mayer, T. M.; Kellerman, B.K.; McIlroy, DT; Howard, A. J.

doi:10.1103/physrevlett.72.3040

Cited by 354 publications

(224 citation statements)

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“…Periodic surface ripples, conical microstructures, whisker-like structures, and pyramidal microstructures have all been observed following high-energy ion-bombardment during sputtering experiments [40,41,42,43,44,45,46,47]. In work that is closely related to our research, conical structures formed after irradiation with nanosecond laser pulses have been observed by several research groups [7,8,10,12,13,14,15,17,48,49,50].…”

Section: Discussionsupporting

confidence: 53%

Microtextured Silicon Surfaces for Detectors, Sensors & Photovoltaics

Carey¹,

Mazur²

2005

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Executive SummaryWith support from this award we studied a novel silicon microtexturing process and its application in silicon-based infrared photodetectors. By irradiating the surface of a silicon wafer with intense femtosecond laser pulses in the presence of certain gases or liquids, the originally shiny, flat surface is transformed into a dark array of microstructures. The resulting microtextured surface has near-unity absorption from near-ultraviolet to infrared wavelengths well below the band gap. The high, broad absorption of microtextured silicon could enable the production of silicon-based photodiodes for use as inexpensive, room-temperature multi-spectral photodetectors. Such detectors would find use in numerous applications including environmental sensors, solar energy, and infrared imaging.The goals of this study were to learn about microtextured surfaces and then develop and test prototype silicon detectors for the visible and infrared. We were extremely successful in achieving our goals. During the first two years of this award, we learned a great deal about how microtextured surfaces form and what leads to their remarkable optical properties. We used this knowledge to build prototype detectors with high sensitivity in both the visible and in the near-infrared. We obtained room-temperature responsivities as high as 100 A/W at 1064 nm, two orders of magnitude higher than standard silicon photodiodes. For wavelengths below the band gap, we obtained responsivities as high as 50 mA/W at 1330 nm and 35 mA/W at 1550 nm, close to the responsivity of InGaAs photodiodes and five orders of magnitude higher than silicon devices in this wavelength region.The following Project Summary includes: Summary of important resultsPrior to receipt of this contract, we developed a process for microtexturing silicon surfaces with laser-assisted etching [1, 2]. The silicon sample is irradiated with a train of high-power ultrashort (100 fs) laser pulses in the presence of SF 6 or Cl 2 . Where the laser strikes the surface, material is etched away in a pattern of conical spikes, with the spike tips at the level of the unetched surface and the spike bases tens of microns below the surface. The surrounding non-irradiated silicon is unaffected, so areas as small as tens of microns on a side can be made. Figure 1 shows a scanning electron micrograph of a microtextured silicon surface.After etching, the silicon surface appears black to the eye (see Figure 2), and the surface absorbs over 90% of incident light from 0.25 µm to 2.5 µm [3]. Flat crystalline silicon absorbs only about 65% of incident light for wavelengths shorter than 1 µm, and absorbs less than 20% at longer wavelengths, with very low absorptance from 1.1 to 1.4 µm. Creation of a prototype microtextured silicon based p-i-n detector.Much of the work done in Year One and Year Two characterized the effects of laser fluence, shot number, gas pressure, and ambient gas on the absorption properties of microtextured silicon [4][5][6][7]. Using this data, we attempted to make...

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Section: Discussionsupporting

confidence: 53%

Microtextured Silicon Surfaces for Detectors, Sensors & Photovoltaics

Carey¹,

Mazur²

2005

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“…In principle, this description should retrieve results for thin layers so that connection with other models [16,17] is feasible in appropriate parameter ranges [22]. Previous experimental [27] and theoretical [28,29] approaches to the IBS problem through the effects of viscous flow are available, although no general description of the process had been achieved so far.…”

Section: Ion-induced Solid Flowmentioning

confidence: 99%

Energy dependence of the ripple wavelength for ion-beam sputtering of silicon: Experiments and theory

Castro¹,

Gago²,

Vázquez³

et al. 2013

AIP Conference Proceedings

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Abstract. In spite of the efforts devoted for the last 20 years to elucidating ion-beam sputtering (IBS) as an instance of surface self-organization, the classic view on the main mechanism inducing the morphological instability has been recently challenged. We report on the verification of a recent theoretical description of this nanopattern formation process for semiconducting targets, as driven by stress-induced, viscous flow of a thin amorphous layer that develops at the surface [M. Cuerno and R. Cuerno, Appl. Surf. Sci. 258, 4171 (2012)]. Through experiments on silicon as a representative case, we study the dependence of the ripple wavelength with the average ion energy, finding a linear dependence in the 0.3-1 keV range. This is explained within the viscous flow framework, taking into account the energy dependence of the number of displaced atoms generated by collision cascades in the amorphous layer, as predicted by previous models of ion-generated stress. For our analysis, we provide a systematic criterion to guarantee actual linear dynamics behavior, not affected by the onset of nonlinear effects that may influence the value of the ripple wavelength.

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“…Many models of the growth of single layers and multilayers have been suggested. 12,13,20 We follow the model in Ref. 11 with several small modifications.…”

Section: Basic Growth Equationsmentioning

confidence: 99%

“…3 The smoothening effects were identified as diffusion and viscous flow. 12 Also, studies have been performed for the modification of bulk materials with ion bombardment, such as SiO 2 , in which it was found that roughening is caused by the removal of atoms. 13,14 In this work the angular as well as the energy dependence of ion bombardment is studied systematically over a wide range, in order to optimize the ion beam parameters with layer thicknesses suitable for practical application, first of all to the reflection of 13.5 nm radiation at near-normal incidence.…”

Section: Introductionmentioning

confidence: 99%

Angular and energy dependence of ion bombardment of Mo/Si multilayers

Voorma

Louis

Bijkerk

et al. 1997

Journal of Applied Physics

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The process of ion bombardment is investigated for the fabrication of Mo/Si multilayer x-ray mirrors using e-beam evaporation. The ion treatment is applied immediately after deposition of each of the Si layers to smoothen the layers by removing an additional thickness of the Si layer. In this study the parameters of Kr ϩ ion bombardment have been optimized within the energy range 300 eV-2 keV and an angular range between 20°and 50°. The optical performance of the Mo/Si multilayers is determined by absolute measurements of the near-normal-incidence reflectivity at 14.4 nm wavelength. The multilayer structures are analyzed further with small-angle reflectivity measurements using both specular reflectivity and diffuse x-ray scattering. The optimal smoothening parameters are obtained by determining the effect of ion bombardment on the interface roughness of the Si layer. The optimal conditions are found to be 2 keV at 50°angle of incidence with respect to the surface. These settings result in 47% reflectivity at 85°( ϭ14.4 nm͒ for a 16-period Mo/Si multilayer mirror, corresponding to an interface roughness of 0.21 nm rms. Analysis shows that the interface roughness is determined by ion induced viscous flow, an effect which increases with ion energy as well as angle of incidence. In order to determine the effect of intermixing of the Si and Mo atoms, the penetration depth of the Kr ϩ ions is calculated as a function of ion energy and angle of incidence. Furthermore, the angular dependence of the etch yield, obtained from the in situ reflectivity measurements, is investigated in order o determine the optimal ion beam parameters for the production of multilayer mirrors on curved substrates. © 1997 American Institute of Physics. ͓S0021-8979͑97͒04716-6͔

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Roughening instability and evolution of the Ge(001) surface during ion sputtering

Cited by 354 publications

References 18 publications

Microtextured Silicon Surfaces for Detectors, Sensors & Photovoltaics

Microtextured Silicon Surfaces for Detectors, Sensors & Photovoltaics

Energy dependence of the ripple wavelength for ion-beam sputtering of silicon: Experiments and theory

Angular and energy dependence of ion bombardment of Mo/Si multilayers

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