CMOS-Compatible and Low-Cost Thin Film MACE Approach for Light-Emitting Si NWs Fabrication

Abstract

Silicon nanowires (Si NWs) are emerging as an innovative building block in several fields, such as microelectronics, energetics, photonics, and sensing. The interest in Si NWs is related to the high surface to volume ratio and the simpler coupling with the industrial flat architecture. In particular, Si NWs emerge as a very promising material to couple the light to silicon. However, with the standard synthesis methods, the realization of quantum-confined Si NWs is very complex and often requires expensive equipment. Metal-Assisted Chemical Etching (MACE) is gaining more and more attention as a novel approach able to guarantee high-quality Si NWs and high density with a cost-effective approach. Our group has recently modified the traditional MACE approach through the use of thin metal films, obtaining a strong control on the optical and structural properties of the Si NWs as a function of the etching process. This method is Complementary Metal-Oxide-Semiconductors (CMOS)-technology compatible, low-cost, and permits us to obtain a high density, and room temperature light-emitting Si NWs due to the quantum confinement effect. A strong control on the Si NWs characteristics may pave the way to a real industrial transfer of this fabrication methodology for both microelectronics and optoelectronics applications.

Silicon Nanowires Synthesis by Metal-Assisted Chemical Etching: A Review

“…The emission of all the samples is reported in Figure 8g, demonstrating their quantum confinement nature. In fact, the PL is redshifted by increasing the average diameter of the Si NWs, in perfect agreement with quantum confinement theory [72,135].…”

“…It is worth to note that H 2 O 2 injects holes into the Si valence band independently of the doping type and level. What changes between different doping type and level is the etching rate of the process [ 72 ]. A MACE process may result in the synthesis of porous Si with different pores dimension or in the fabrication of Si NWs.…”

“…Different metals were employed in these years as a catalyst during a MACE approach such as Ag [ 113 , 132 , 136 , 137 ], Au [ 64 , 72 , 102 , 115 ], Pt [ 104 ], Ni [ 103 ], Cu [ 123 ], W [ 102 ]. The most used one remains the gold due to the best quality of fabricated Si NWs, for the stability in the etching solution compared to the silver, and for the fast and high tunable etching rate compared to other metals.…”

Probing two-level systems with electron spin inversion recovery of defects at the Si/SiO2 interface

“…For both samples, any residual metal impurities are expected to remain close to the tips of the nanowires, therefore, affecting less than 0.2% of the DBs that we probe experimentally. The metal contamination in SiNWs produced by MACE, in contrast with those produced by the vaporliquid-solid method with a metal catalyst, has been found negligible by different experimental methods [21][22][23][24]. The full process led to a dense carpet of straight silicon nanowires, fully passivated with H and with structural parameters dependent on the process details ( Fig.…”

Ultrathin Silicon Nanowires for Optical and Electrical Nitrogen Dioxide Detection

“…Indeed, as far as the authors know, no case of gas sensing devices based on Si NW light emission are reported in the literature. Recently, our group demonstrates the use of a modified Metal-Assisted Chemical Etching (MACE) process, by using ultra-thin gold (Au) films to synthesize RT light-emitting Si NWs [ 56 ] due to the quantum confinement effect, as already investigated in our works [ 57 , 58 , 59 , 60 , 61 , 62 ]. This approach is industrially compatible, maskless, and cost-effective.…”