Self-Oscillated Growth Formation of Standing Ultrathin Nanosheets out of Uniform Ge/Si Superlattice Nanowires

Self-oscillation is an intriguing and omnipresent phenomenon that governs a broad range of growth dynamics and formation of nanoscale periodic and delicate heterostructures.A self-oscillating growth phenomenon of catalyst droplets,consuming surface-coating a-Si/a-Ge bilayer,is exploited to accomplish a high-frequency alternating growth of ultrathin crystalline Si and Ge(c-Si/c-Ge)nano-slates,with Ge-rich layer thickness of 14–19 nm,embedded within a superlattice nanowire structure,with pre-known position and uniform channel diameter.A subsequent selective etching of the Ge-rich segments leaves a chain of ultrafine standing c-Si nanosheets down to~6 nm thick,without the use of any expensive high-resolution lithography and growth modulation control.A ternary-phase-competition model has been established to explain the underlying formation mechanism of this nanoscale self-oscillating growth dynamics.It is also suggested that these ultrathin nanosheets could help to produce ultrathin fin-channels for advanced electronics,or provide size-specified trapping sites to capture and position hetero nanoparticle for high-precision labelling or light emission.

Ultrathin 3D radial tandem‐junction photocathode with a high onset potential of 1.15 V for solar hydrogen production

Combining a progressive tandem junction design with a unique Si nanowire(SiNW)framework paves the way for the development of high‐onset‐potential photocathodes and enhancement of solar hydrogen production.Herein,a radial tandem junction(RTJ)thin film water‐splitting photo‐cathode has been demonstrated experimentally for the first time.The photocathode is directly fab‐ricated on vapor‐liquid‐solid‐grown SiNWs and consists of two radially stacked p‐i‐n junctions,featuring hydrogenated amorphous silicon(a‐Si:H)as the outer absorber layer,which absorbs short wavelengths,and hydrogenated amorphous silicon germanium(a‐SiGe:H)as the inner layer,which absorbs long wavelengths.The randomly distributed SiNW framework enables highly efficient light‐trapping,which facilitates the use of very thin absorber layers of a‐Si:H(~50 nm)and a‐SiGe:H(~40 nm).In a neutral electrolyte(pH=7),the three‐dimensional(3D)RTJ photocathode delivers a high photocurrent onset of 1.15 V vs.the reversible hydrogen electrode(RHE),accompanied by a photocurrent of 2.98 mA/cm^(2) at 0 V vs.RHE,and an overall applied‐bias photon‐to‐current effi‐ciency of 1.72%.These results emphasize the promising role of 3D radial tandem technology in developing a new generation of durable,low‐cost,high‐onset‐potential photocathodes capable of large‐scale implementation。

Boundedness of some integral operators and commutators on homogeneous Herz spaces with three variable exponents

We obtain the boundedness of some integral operators and commutators on homogeneous Herz spaces with three variable exponents K^(˙α(⋅))_(p(⋅),q(⋅)),such as some sublinear operators,the fractional integral and its commutator.