Integrated Circuit Bonding Distance Inspection via Hierarchical Measurement Structure.

Bonding distance is defined by the projected distance on a substrate plane between two solder points of a bonding wire, which can directly affect the morphology of the bonding wire and the performance between internal components of the chip. For the inspection of the bonding distance, it is necessary to accurately recognize gold wires and solder points within the complex imagery of the chip. However, bonding wires at arbitrary angles and small-sized solder points are densely distributed across the complex background of bonding images. These characteristics pose challenges for conventional image detection and deep learning methods to effectively recognize and measure the bonding distances. In this paper, we present a novel method to measure bonding distance using a hierarchical measurement structure. First, we employ an image acquisition device to capture surface images of integrated circuits and use multi-layer convolution to coarsely locate the bonding region and remove redundant background. Second, we apply a multi-branch wire bonding inspection network for detecting bonding spots and segmenting gold wire. This network includes a fine location branch that utilizes low-level features to enhance detection accuracy for small bonding spots and a gold wire segmentation branch that incorporates an edge branch to effectively extract edge information. Finally, we use the bonding distance measurement module to develop four types of gold wire distribution models for bonding spot matching. Together, these modules create a fully automated method for measuring bonding distances in integrated circuits. The effectiveness of the proposed modules and overall framework has been validated through comprehensive experiments.

Activating Three-Dimensional Networks of Fe@Ni Nanofibers via Fast Surface Modification for Efficient Overall Water Splitting.

Developing facile approaches to synthesize highly active and stable oxygen and hydrogen evolution electrocatalysts under mild conditions is crucial in water-splitting technology. Herein, Ni-nanofiber-based three-dimensional (3D) network is prepared by a magnetic-field-assisted reduction reaction and then a fast surface modification within only 3 s at room temperature is developed to prepare Fe@Ni-nanofiber-based 3D porous electrode. The unique structure of the nanofiber-based 3D electrode ensures large electrochemical active surface area, short electron diffusion pathway, and fast mass transportation, while the introduction of Fe enhances the activity of each active site with abundant Ni(Fe) (oxy)hydroxide on the surface. Hence, the obtained Fe@Ni nanofiber electrode exhibits excellent activity and stability toward oxygen evolution reaction and hydrogen evolution reaction, with overpotentials as low as 230 and 55 mV to achieve a current density of 10 mA cm-2 in alkaline electrolyte, respectively. Moreover, when assembled into a two-electrode configuration, the cell voltage of only 1.53 V is needed to drive the water-splitting cell at 10 mA cm-2.

Decoration of reduced graphene oxide by gold nanoparticles: an enhanced negative photoconductivity.

Photodetection in a visible light region is important in various applications, including computation, environmental monitoring, biological detection and industrial control. Due to this, research studies to develop photoconductive devices have great significance. We report a study on the photoconductivity of reduced graphene oxide (rGO)/gold nanoparticle (AuNP) nanocomposites, emphasizing the enhancement effect induced by AuNPs. rGO/AuNP photoelectric devices were prepared by spincoating rGO onto an AuNP-array-covered silicon substrate. Photoelectric responses under visible light illumination were measured and the results showed that the negative photoelectric responsivity of rGO was improved by 3 orders of magnitude due to AuNPs. The effects of AuNPs on negative photoconductivity (NPC) properties of rGO were investigated, and it was found that AuNPs affected NPC in three aspects: (1) AuNPs form discrete electrodes separated by nanoscale gaps which generated new conduction paths, and hence the conductivity of rGO was enhanced by 3 orders of magnitude; (2) localized surface plasmon resonance (LSPR) of AuNPs effectively enhances total light absorption of rGO; (3) photocurrent between AuNPs and rGO can weaken the NPC property of rGO. The low-cost and mass-producible rGO/AuNP nanocomposites demonstrate high photoelectric responsivity, which hold much promise for NPC devices.

Calibrating conservative and dissipative response of electrically-driven quartz tuning forks.

Determining sensor parameters is a prerequisite for quantitative force measurement. Here we report a direct, high-precision calibration method for quartz tuning fork (TF) sensors that are popular in the field of nanomechanical measurement. In the method, conservative and dissipative forces with controlled amplitudes are applied to one prong of TF directly to mimic the tip-sample interaction, and the responses of the sensor are measured at the same time to extract sensor parameters. The method, for the first time, allows force gradient and damping coefficient which correspond to the conservative and dissipative interactions to be measured simultaneously. The calibration result shows surprisingly that, unlike cantilevers, the frequency shift for TFs depends on both the conservative and dissipative forces, which may be ascribed to the complex dynamics. The effectiveness of the method is testified by force spectrum measurement with a calibrated TF. The method is generic for all kinds of sensors used for non-contact atomic force microscopy (NC-AFM) and is an important improvement for quantitative nanomechanical measurement.

Biomimic Hairy Skin Tactile Sensor Based on Ferromagnetic Microwires.

We present a multifunctional tactile sensor inspired by human hairy skin structure, in which the sensitive hair sensor and the robust skin sensor are integrated into a single device via a pair of Co-based ferromagnetic microwire arrays in a very simple manner. The sensor possesses a self-tunable effective compliance with respect to the magnitude of the stimulus, allowing a wide range of loading force to be measured. The sensor also exhibits some amazing functions, such as air-flow detection, material property characterization, and excellent damage resistance. The novel sensing mechanism and structure provide a new strategy for designing multifunctional tactile sensors and show great potential applications on intelligent robot and sensing in harsh environments.

Oxidative etching of MoS2/WS2 nanosheets to their QDs by facile UV irradiation.

Oxidative etching has been proved to be an efficient top-down method to prepare quantum dots (QDs) of layered transition-metal dichalcogenides which possess unique properties and have potential applications in various areas. Here, one facile and green oxidative etching method induced by UV irradiation is reported to prepare the QDs of MoS2/WS2 in aqueous solution, respectively. A prominent morphology change occurred to the nanosheets of MoS2/WS2 after irradiation and finally they were etched to ultrasmall nanoparticles which were proved to be the QDs. Insight into the etching mechanism was discussed in detail and hydroxyl free radicals (˙OH) were conclusively demonstrated to play the main role in etching nanosheets. From another point of view, this work also proves the crucial long-term photo instability of MoS2/WS2 since there are increasing photo-related applications of them and points out an easy way to degrade their nanosheets.

Note: Wide band amplifier for quartz tuning fork sensors with digitally controlled stray capacitance compensation.

We presented a preamplifier design for quartz tuning fork (QTF) sensors in which the stray capacitance is digitally compensated. In this design, the manually controlled variable capacitor is replaced by a pair of varicap diodes, whose capacitance could be accurately tuned by a bias voltage. A tuning circuit including a single side low power operational amplifier, a digital-to-analog converter, and a microprocessor is also described, and the tuning process can be conveniently carried out on a personal computer. For the design, the noise level was investigated experimentally.

Starburst triarylamine based dyes bearing a 3,4-ethylenedioxythiophene linker for efficient dye-sensitized solar cells.

Starburst triarylamine-based organic dyes (D1, D2, and D3) have been synthesized. For the three designed dyes, the starburst triarylamine group, thiophene (or 3,4-ethylenedioxythiophene), and cyanoacetic acid take the role of electron donor, π-conjugation bridge, and electron acceptor, respectively. These compounds are characterized by photophysical, electrochemical, and theoretical computational methods. Nanocrystalline TiO2-based dye-sensitized solar cells were fabricated using these molecules as light-harvesting sensitizers. The overall efficiencies of the sensitized cells range from 5.48 to 6.15%. It was found that the introduction of the EDOT group in D3 bathochromically extended the absorption spectra, resulting in a leap in the photovoltaic performance in comparison to D2. Incorporation of a hydrophobic carbazole-containing segment at D2 relative with D1 retarded the electron transfer from TiO2 to the oxidized dye or electrolyte, leading to an increase of electron lifetime.

Minority carrier effects in nanoscale Schottky contacts.

We report the current-voltage behavior for nanoscale point contacts to Si(111) obtained in ultrahigh vacuum using scanning tunneling microscopy. Epitaxial CoSi(2) islands provide single-crystal contacts with well-defined size and shape. The zero bias conductance is found to be independent of the island size (10(2)-10(4) nm(2)) and shape, but varies strongly with the surface Fermi level position. This behavior is explained by the recombination-generation current from minority carriers at the free surface, which may be orders of magnitude larger than the majority carrier thermionic or tunnel currents across the contact interface. This can give rise to large shifts of the apparent ideality factor and Schottky barrier height for the point contact.