Wafer-scale fabrication of isolated luminescent silicon quantum dots using standard CMOS technology

A wafer-scale fabrication method for isolated silicon quantum dots (Si QDs) using standard CMOS technology is presented. Reactive ion etching was performed on the device layer of a silicon-on-insulator wafer, creating nano-sized silicon islands. Subsequently, the wafer was annealed at 1100 °C for 1 h in an atmosphere of 5% H₂ in Ar, forming a thin oxide passivating layer due to trace amounts of oxygen. Isolated Si QDs covering large areas (∼mm²) were revealed by photoluminescence (PL) measurements. The emission energies of such Si QDs can span over a broad range, from 1.3 to 2.0 eV and each dot is typically characterized by a single emission line at low temperatures. Most of the Si QDs exhibited a high degree of linear polarization along Si crystallographic directions [[Formula: see text]] and [[Formula: see text]]. In addition, system resolution-limited (250 μeV) PL linewidths (full width at half maximum) were measured for several Si QDs at 10 K, with no clear correlation between emission energy and polarization. The initial part of PL decays was measured at room temperature for such oxide-embedded Si QDs, approximately several microseconds long. By providing direct access to a broad size range of isolated Si QDs on a wafer, this technique paves the way for the future fabrication of photonic structures with Si QDs, which can potentially be used as single-photon sources with a long coherence length.

Wafer-level fabrication of individual solid-state nanopores for sensing single DNAs

For biomolecule sensing purposes a solid-state nanopore platform based on silicon has certain advantages as compared to nanopores on other substrates such as graphene, silicon nitride, silicon oxide etc Capitalizing on the developed CMOS technology, nanopores on silicon are scalable without any requirement for additional processing, the devices are low cost and the process can be repeatable with a high yield. One of the essential requirements in biomolecule sensing is the ability of the nanopore to interact with the analyte. In this work, we present a method for processing high aspect ratio, single nanopores in the range of 10-30 nm in diameter and approximately 700 nm in length on a silicon-on-insulator (SOI) wafer. The presented method of manufacturing the high aspect ratio individual nanopores combines optical lithography and anisotropic KOH etching with a final electrochemical etching step to form the nanopores and is repeatable and can be processed in batches. We demonstrate electrical detection of dsDNA translocation, where the characteristic time of the process is in the millisecond range. We also analyse the translocation parameters and correlate the enhanced length of the nanopore to a longer translocation time as compared to other substrates.

Label-Free Surface Protein Profiling of Extracellular Vesicles by an Electrokinetic Sensor

Small extracellular vesicles (sEVs) generated from the endolysosomal system, often referred to as exosomes, have attracted interest as a suitable biomarker for cancer diagnostics, as they carry valuable biological information and reflect their cells of origin. Herein, we propose a simple and inexpensive electrical method for label-free detection and profiling of sEVs in the size range of exosomes. The detection method is based on the electrokinetic principle, where the change in the streaming current is monitored as the surface markers of the sEVs interact with the affinity reagents immobilized on the inner surface of a silica microcapillary. As a proof-of-concept, we detected sEVs derived from the non-small-cell lung cancer (NSCLC) cell line H1975 for a set of representative surface markers, such as epidermal growth factor receptor (EGFR), CD9, and CD63. The detection sensitivity was estimated to be ∼175000 sEVs, which represents a sensor surface coverage of only 0.04%. We further validated the ability of the sensor to measure the expression level of a membrane protein by using sEVs displaying artificially altered expressions of EGFR and CD63, which were derived from NSCLC and human embryonic kidney (HEK) 293T cells, respectively. The analysis revealed that the changes in EGFR and CD63 expressions in sEVs can be detected with a sensitivity in the order of 10% and 3%, respectively, of their parental cell expressions. The method can be easily parallelized and combined with existing microfluidic-based EV isolation technologies, allowing for rapid detection and monitoring of sEVs for cancer diagnosis.

Pt-Al2O3 dual layer atomic layer deposition coating in high aspect ratio nanopores

Functional nanoporous materials are promising for a number of applications ranging from selective biofiltration to fuel cell electrodes. This work reports the functionalization of nanoporous membranes using atomic layer deposition (ALD). ALD is used to conformally deposit platinum (Pt) and aluminum oxide (Al(2)O(3)) on Pt in nanopores to form a metal-insulator stack inside the nanopore. Deposition of these materials inside nanopores allows the addition of extra functionalities to nanoporous materials such as anodic aluminum oxide (AAO) membranes. Conformal deposition of Pt on such materials enables increased performances for electrochemical sensing applications or fuel cell electrodes. An additional conformal Al(2)O(3) layer on such a Pt film forms a metal-insulator-electrolyte system, enabling field effect control of the nanofluidic properties of the membrane. This opens novel possibilities in electrically controlled biofiltration. In this work, the deposition of these two materials on AAO membranes is investigated theoretically and experimentally. Successful process parameters are proposed for a reliable and cost-effective conformal deposition on high aspect ratio three-dimensional nanostructures. A device consisting of a silicon chip supporting an AAO membrane of 6 mm diameter and 1.3 μm thickness with 80 nm diameter pores is fabricated. The pore diameter is reduced to 40 nm by a conformal deposition of 11 nm Pt and 9 nm Al(2)O(3) using ALD.