Field emission properties of p-type black silicon on pillar structures

Abstract

Arrays of black silicon field emission pillar structures were fabricated on p-type silicon substrates. Two types of samples with the same number of pillars (arrays of 10 × 10) but different pillar heights (8 and 20 μm) were prepared as well as a black silicon reference sample without pillars. The field emission properties of these cathodes were investigated both by means of integral current-voltage measurements and by field emission scanning microscopy. Samples with a pillar height of 20 μm revealed onset fields as low as 6.4 V/μm, field enhancement factors up to 800, and emission currents up to 8 μA at an applied field of 20 V/μm. Due to the p-type material, a saturation of the emission current for fields above 11 V/μm was observed. This saturation leads to a stable operation with a current fluctuation of less than ±8%. It was found that samples with a pillar height of 20 μm showed improved emission characteristics compared to samples with a pillar height of 8 μm or without pillars. The voltage maps revealed an increased emission homogeneity after a “burn-in” sequence of the sample. The current map showed that a few of the pillars dominate the emission. Integral current stability measurements were performed under different vacuum pressures, in order to investigate altered emission behavior and a potential degradation of the emitters. At pressures above 10−6 mbar, the sample starts to degrade irreversibly. Nevertheless, even after a harsh treatment over 30 min at 5 × 10−5 mbar and at an applied field of 23 V/μm, the cathode was still operating, and did not fail during further operation over 20 h at 5 × 10−8 mbar and at an applied field of 28 V/μm.

Black-Si as a Photoelectrode

“…The nanotexturing of silicon (Si) to endow the surface topography with a random array of high-aspect-ratio spikes that can efficiently trap light (enhancing absorption, since reflection is suppressed) due to a gradual refractive index change-known as b-Si [1]-has demonstrated a wide range of useful properties: b-Si acts as an anti-reflection surface over the VIS-IR spectral range, exhibits efficient bactericidal activity towards gram-positive and gram-negative bacteria [2] (Figure 1a), can rupture the soft membranes of red blood cells [3], acts as a field emitter electrode [4], can be used as a substrate for surface enhanced Raman sensing/spectroscopy (SERS) [5], and has application in solar cell technology [6,7]. Additionally, the optical binding/trapping of small particles on b-Si was recently demonstrated at very high laser powers when the nonlinear optical effects inside the trapped material could be induced [8].…”

Magnetically enhanced photoconductive high voltage control

“…Under illumination, the resistivity of cathodes fabricated from intrinsically doped n-type and p-type silicon fall to as low as 0.005 Xm and 1 to 10 Xcm, respectively (Langer et al 2014). The reduced resistivity can be evoked through pulsed laser irradiation of the silicon surface resulting in current flows in the nA to low lA ranges (Langer et al 2016). However, at larger scales and normal atmospheric pressure, implementation becomes a problem.…”

Black-Si as Photoelectrode

“…Nanotextured silicon -Black-Si [1] -has a range of useful properties: it acts as an antireflection surface over the vis-IR spectral range, has bactericidal activity against gram positive and negative bacteria [2] (Fig. 1(a)), can rupture soft membranes of red blood cells [3], can act as a field emitter electrode [4], can be rendered into a hydrophobic surface, substrates for surface enhanced Raman sensors/spectroscopy (SERS) [5] and it is used for solar cells [6,7]. Recently, optical binding/trapping of Black-Si was demonstrated at very high laser powers when nonlinear optical effects inside trapped material can be induced [8].…”