High power density laser etching of silicon

Abstract

Single beam determination of porosity and etch rate in situ during etching of porous siliconSilicon that was immersed in hydrofluoric acid can be etched photochemically by laser, and it is found to produce long and regular columnar structure if the laser power density is greater than 10 mW/mm 2 . Another criterion is that the laser wavelength should be at the blue end of the visible spectrum. Fine wires with diameter 300-200 nm were also observed at the top of these columns. The dimension of these fine wires is near to quantum confinement dimension and thus can be taken as supporting evidence for quantum confinement. The photoluminescence spectra full width half maximum was narrower than that from porous silicon fabricated from the conventional anodization method. The narrower full width was attributed to the uniformity of the porous silicon structure. A physical model is proposed to explain the observed strong directional etching. The model showed that once the etch sites have been randomly initiated, the etching rate becomes directional under the influence of the laser. The intensity of the laser controls the etching direction such that silicon columns are formed if the intensity of the laser is strong enough.

Pulsed-laser micropatterned quantum-dot array for white light source

“…In this paper, we exploit the pulsed laser direct writing and aerosol jet (AJ) spray coating techniques to develop a novel photoluminescent quantum dots device with microscale patterns for the uses as a white light emitting source 14 . The pulsed laser ablation technique 15 16 17 was employed to directly fabricate microscale square holes with nano-ripple structures onto the sapphire substrate of a flip-chip blue light-emitting diode, confining sprayed quantum dots into well-defined areas and eliminating the coffee ring effect. The AJ spray coating method is a mask-free technique and can be used to reduce the volume of QD films, decrease the consumption of QDs, and easily deposit QDs on target areas with determined QDs proportions 18 .…”

Laser-induced etching parameters impact on optical properties of the silicon nanostructures

“…The pores over structure were not clearly defined at laser power density of 6 W/cm 2 as shown in Figure 2(b). The chemical reaction was initiated at laser power density of 12 W/cm 2 , but due to the insufficient structure interaction, the etched area was irregular as shown in Figure 2(c), which meant that electron-hole pairs generated were insufficient [9,10]. Micro columns existed on the surface when laser power density was increased to 25 W/cm 2 as shown in Figure 2(d).…”

Photoluminescence and AFM characterisation of photochemically etched highly resistive n‐type silicon

“…Ngan et al [8] and Wellner et al [9] used SEM (Scanning Electron Microscopy) and TEM (Transmission Electron Microscopy) , respectively, to investigate the surface structure. Note that this method was less studied for the reason that the results were not reproducible.…”