Peripheral Nanostructured Porous Silicon Boosts Static and Dynamic Performance of Integrated Electronic Devices

Abstract

Porous silicon (PSi) is a nano-to microstructured form of silicon achieved by anodic etching of a conventional silicon wafer in acidic electrolytes. [20] Since the discovery of quantum-confinement room temperature luminescence from porous silicon, [21] nanostructured porous silicon (n-PSi) has greatly attracted the attention of researchers, who dreamed of an all-silicon photonics where electronic circuits and light emitting devices were integrated together in a silicon chip. [22] As the difficulties in increasing and stabilizing light emission of n-PSi LEDs soon became apparent, reports on the modulation of bulk-silicon properties (e.g., mechanical, thermal, electrical, optical, and biochemical) through reduction to its n-PSi form [23] have sustained porous silicon research over the following years, opening new opportunities toward unexpected applications. For instance, the thermal conductivity of n-PSi can be reduced over 3 decades with respect to that of crystalline silicon (c-Si). [23,24] The low thermal conductivity of n-PSi together with a reduced heat capacitance have enabled the fabrication of thermally induced ultrasonic transducers using n-PSi as a displacement-free (i.e., nonpiezoelectric) emitter. [25] The refractive index of n-PSi can be finely tuned from that of c-Si to that of air (almost). [26] The lower n-PSi refraction index, with respect to that of c-Si, has enabled the fabrication of label-free optical biosensors exploiting back-scattered n-PSi interferometers. [27-29] Bioresorbability of n-PSi can be tuned from hours to months in physiological conditions. [23] The tunable bioresorbability of n-PSi together with its biocompatibility and photoluminescence have enabled the preparation of drug-loaded self-reporting PSi nanoparticles for medical applications. [30,31] Among electrical properties, mobility and lifetime of charge carriers in n-PSi have been also reported to be tunable with respect to that of c-Si. [32,33] The mobility of charge carriers in n-PSi was shown to reduce down to a factor 10 6 with respect to that of bulk silicon. [32] The complex structural network of silicon nanocrystallites of n-PSi produces a strong spatial dispersion of drifting carriers over multiple paths different in length and geometry, which is responsible for the strong reduction of the mobility of both electrons and holes. [32] Recent fundamental studies on n-PSi further highlighted how the lifetime Nanomaterials hold the promise of revolutionizing electronics and, in turn, its applications, thanks to the unique properties of charge carriers traveling in structures with length scale down to a few nanometers. Here, the tremendous reduction of mobility and lifetime of charge carriers when traveling in randomly arranged nanostructured silicon crystallites, namely, nanostructured porous silicon (n-PSi), is leveraged to simultaneously improve the turn-off switching speed and reverse operation voltage of solid-state devices integrated nearby. As a proof-of-concept application, it is shown that the integration of periph...

Research on Processing Technology of Multi-Layer Heterogeneous Material Composite Micron Cantilever Beam Structure

“…Generally, photoresist, SiO 2 , or porous silicon are used as the sacrificial layer to realize the release of the suspended structure. The production of porous silicon is simpler than other methods [17][18][19]. Due to its controllable porosity and thickness and high removal selectivity, porous silicon is used as the sacrificial layer in this article.…”

The effective of time etching and different acids on the morphological porous silicon

“…Where q is silicon density (2.3 g/cm 3 ), S (cm 3 ) is the etched surface area 13 . This method is called Gravimetric measurements.…”

Vapor‐Phase Synthesis of Molecularly Imprinted Polymers on Nanostructured Materials at Room‐Temperature

“…[37][38][39][40] PSiO 2 acts not only as nanostructured scaffold but also as optical transducer thus demonstrating the advantage of the vaporphase approach enabling nanostructured MIP synthesis and integration with the transducer in a single step with no need of additional steps for scaffold removal and/or integration with the transducer, contrarily to what observed in other imprinting approaches for MIP nanostructuring. [22,41] Further, PSi has been increasingly exploited in optical (bio)sensing with organic bioreceptors, [42][43][44][45][46][47] thanks to the facile preparation of different optical structures (i.e., interferometers, [42,45,[48][49][50] resonant cavities, [51][52][53] and waveguides [54][55][56][57] ), high effective surface for the accommodation of receptors and target molecules (i.e., proteins, [44,45] DNA, [56,58,59] and drugs [60][61][62] ), intrinsic nanoscale filtering that enables operation of PSi sensors with complex biological fluids (i.e., saliva, [46,42] blood, [63,64] and interstitial fluid [65] ).…”