Composition and conductance distributions of single GeSi quantum rings studied by conductive atomic force microscopy combined with selective chemical etching

Abstract

Atomic force microscopy imaging combined with selective chemical etching is employed to quantitatively investigate three-dimensional (3D) composition distributions of single GeSi quantum rings (QRs). In addition, the 3D quantitative composition distributions and the corresponding conductance distributions are simultaneously obtained on the same single GeSi QRs by conductive atomic force microscopy combined with selective chemical etching, allowing us to investigate the correlations between the conductance and composition distributions of single QRs. The results show that the QRs' central holes have higher Ge content, but exhibit lower conductance, indicating that the QRs' conductance distribution is not consistent with their composition distribution. By comparing the topography, composition and conductance profiles of the same single QRs before and after different etching processes, it is found that the conductance distributions of GeSi QRs do not vary with the change of composition distribution. Instead, the QRs' conductance distributions are found to be consistent with their topographic shapes, which can be supposed to be due to the shape determined electronic structures.

Investigating the Composition and Conductance Distributions on Highly GeSi Mixed Quantum Dots and Inside Oxidation Problem

“…Furthermore, the contact area between the tip and dot surface is also larger at the periphery, forming ring-shaped current distribution. Since the dome-shaped QDs with different GeSi compositions (after different etching processes) exhibit similar ring-shaped current distribution, it can de declared that the QDs’ current distribution is mainly determined by its topography, while the current values are greatly influenced by the Ge content, similar to the conclusion obtained on GeSi quantum rings [ 33 , 37 ].…”

“…To reduce the influence of local anode oxidation, the current images were measured at negative sample biases and all experiments were performed in a flowing nitrogen atmosphere. To realize the measurements on the same QDs before and after etching, a nanoscale trench with more than 20 nm in depth was made by the AFM tip during scanning, as introduced in our previous work [ 33 ]. As the bottom of the trench reaches the pure Si buffer layer, it can hardly be etched in NHH solution since the etching rate decreases to be smaller than 0.01 nm/min for pure Si [ 20 , 21 ] and hence can act as a better height benchmark than the wetting layer (WL).…”

Probing switching mechanism of memristor for neuromorphic computing

“…For some time after its invention, CAFM is usually used to study ultra-thin dielectrics (especially high dielectric constant materials [62]) and some related phenomena. With the continuous development of technology, nanomaterials (such as quantum dots [82], nanowires [83], 2D materials [33], etc) and electronic phenomena (such as piezoelectricity [84], photoelectricity [85], ferroelectricity [86], etc) are also analyzed. In sum, CAFM can be used to collect topographic and current maps simultaneously and independently.…”

A rapid and automated relocation method of an AFM probe for high-resolution imaging

“…However, the resolution of an optical microscope is generally no more than 200 nm owing to limitations associated with the wavelength of visible light [13], meaning that nanoscale objects or structures cannot be effectively identified by an optical microscope. Meanwhile, owing to the different dimensions of the different types of probes, as well as the installation deviation of probes on the probe clamp, it is extremely challenging to precisely relocate the AFM probe to the initial scan/manipulation area for the same nano target after the AFM probe has been replaced or the sample has been removed [14][15][16][17]. For example, it is possible that the sample requires a scanning electron microscope (SEM) for observation and analysis, or that the sample needs to be treated by a process such as annealing in a chemical vapor deposition (CVD) chamber.…”