In this study, ZnO/ZnS nanocomposite-based dual UV light/CO gas sensing devices have been demonstrated for the first time. To characterize the nanocomposites, multiple material characterizations ...indicated ZnS/ZnO core-shell rods were successfully formed on SiO 2 substrates. Moreover, CO gas sensing and UV light detection measurements both revealed that incorporation of a ZnS shell on ZnO nanorods (NRs) can effectively increase gas sensing and light detection capabilities. Owing to their compact size, low cost, and simple fabrication, ZnO/ZnS NR-based gas and light dual-sensing devices show promises in hazardous gas and light monitoring.
The thermal expansion behavior of Cu plays a critical role in the bonding mechanism of Cu/SiO
hybrid joints. In this study, artificial voids, which were observed to evolve using a focused ion beam, ...were introduced at the bonded interfaces to investigate the influence of compressive stress on bonding quality and mechanisms at elevated temperatures of 250 °C and 300 °C. The evolution of interfacial voids serves as a key indicator for assessing bonding quality. We quantified the bonding fraction and void fraction to characterize the bonding interface and found a notable increase in the bonding fraction and a corresponding decrease in the void fraction with increasing compressive stress levels. This is primarily attributed to the Cu film exhibiting greater creep/elastic deformation under higher compressive stress conditions. Furthermore, these experimental findings are supported by the surface diffusion creep model. Therefore, our study confirms that compressive stress affects the Cu-Cu bonding interface, emphasizing the need to consider the depth of Cu joints during process design.
In this study, 2-D graphene was integrated with zinc oxide (ZnO) nanorods (NRs) to form broadband photo/gas dual sensors. Since ZnO-based photodetectors (PDs) perform excellent in ultraviolet (UV) ...light detection, their inability to sense long-wavelength visible and infrared (IR) light limits the PDs' applications. By combining a 2-D graphene layer on ZnO NRs, the 2-D graphene extended light detection range of device from UV to IR light. In terms of gas sensing, this ZnO NR/graphene-based sensor was capable of sensing hydrogen (H2) carbon monoxide (CO) gases. This device exposed to H2 and CO gases delivered comparable sensitivity of 0.25 under an operated temperature of 300 °C. Multiple material characterizations confirm that a 2-D graphene layer has successfully deposited on ZnO NRs to form a distinct hybrid ZnO NR/graphene nanostructure. Through a series of sensing analyses, results have been demonstrated that the ZnO NR/graphene-based sensor outperformed ZnO-based sensor in response to light illumination. However, ZnO NR/graphene-based sensor exhibited inferior gas sensitivity than the ZnO-based sensor. The coverage of graphene on the surface of ZnO NRs could passivate the surface defects of ZnO NRs. Although the surface passivation was beneficial for reducing the charge recombination and improving the photocurrent, the surface passivation of graphene reduced the adsorption sites of target gas. As a result, the gas sensitivity of ZnO NR/graphene-based sensor was reduced. Although the ZnO NR/graphene-based sensor exhibited a reduced gas sensitivity, the hybrid ZnO/2-D graphene nanocomposites pave the way for broadband PDs and gas sensors with promising applications in various fields.
Al/InGaAs, Al/Ti/InGaAs, and Al/Ni/InGaAs contacts were prepared by conducting rapid thermal annealing at different temperatures, and the interfacial reaction was characterized using x-ray ...diffraction, atomic force microscopy, and transmission electron microscopy. The specific contact resistivity of the metal film contacts on
n
-InGaAs was determined using a circular transmission line measurement. The Al/Ni/InGaAs, Al/Ti/InGaAs, and Al/InGaAs stack contacts remained stable even after the samples were subjected to annealing at 400°C. When the annealing temperature increased to 600°C, Al began melting and clustering due to the formation of Al(Ga) to form Al/InGaAs. An AlNi phase was formed at the interfaces of an Al/Ni/InGaAs contact when it was annealed above 400°C, thus causing the specific resistance and roughness to increase dramatically. Each element of the Al/Ti/InGaAs contact began diffusing when it was annealed beyond 400°C, and an Al
3
Ti phase was formed above 500°C. The formation of Al
3
Ti led to the increase in the specific resistance and roughness. Moreover, the as-deposited Al/Ni/InGaAs, Al/Ti/InGaAs and Al/InGaAs samples had specific resistances of 1.11 × 10
−5
Ω cm
2
, 5.11 × 10
−5
Ω cm
2
, and 1.14 × 10
−4
Ω cm
2
, respectively. These results reveal that to develop the Al/Ti/InGaAs and Al/Ni/InGaAs stacks on InGaAs with a low parasitic resistance, the processing temperature should be lower than 400°C.
For decades, Moore's Law has neared its limits, posing significant challenges to further scaling it down. A promising avenue for extending Moore's Law lies in three-dimensional integrated circuits ...(3D ICs), wherein multiple interconnected device layers are vertically bonded using Cu-Cu bonding. The primary bonding mechanism involves Cu solid diffusion bonding. However, the atomic diffusion rate is notably low at temperatures below 300 °C, maintaining a clear and distinct weak bonding interface, which, in turn, gives rise to reliability issues. In this study, a new method of surface modification using epoxy resin to form fine grains on a nanotwinned Cu film was proposed. When bonded at 250 °C, the interfacial grains grew significantly into both sides of the Cu film. When bonded at 300 °C, the interfacial grains extended extensively, eventually eliminating the original bonding interface.
A high-quality and highly-transparent AlN template was prepared by regrowth on a
sputter-deposited AlN
buffer layer. The
buffer layer was
thermally annealed and then underwent AlN regrowth in ...metalorganic chemical vapor deposition
(MOCVD). The
peakwidth of (002) and (102) plane x-ray rocking curve was 104 arcsec and 290 arcsec,
respectively, indicating a threading dislocation density <5.0 × 108
cm−2. Dislocations were reduced via grain growth and morphological
evolution. The absence of carbon impurity source in sputter deposition also resulted in an
improved transparency. According to transmission and reflection measurements, the
absorption rate
of λ=280 nm emission propagating through the template was less than 6%.
•ZnO/ZnS core-shell structures were deposited on glass substrate.•Multiple material characterizations were performed on nanostructures.•Crystalline phases were examined on the whole chip and certain ...locations.•Element compositions were evaluated on the whole chip and certain locations.
ZnO/ZnS core-shell nanostructures were hydrothermally fabricated on glass substrates. Multiple material characterizations were used to examine the nanostructures. Results indicate that a ZnS shell with a thickness around 10 nm could be viewed on the ZnO/ZnS core-shell structures. Furthermore, different crystalline phases and element compositions in different locations around nearby nanostructures could be found in selected area diffraction patterns and energy dispersive X-ray spectroscopy. ZnS/ZnO nanostructures on glass substrates show promise for future optoelectronic and electronic device applications.
Potassium hydroxide solution was used to etch un-doped GaN grown on the sapphire substrate at 180 and 260 °C. We illustrated the etching phenomenon in detail and probed its mechanism in the wet ...etching process. By multiplying the planar density and the number of dangling bonds on the N atom, we proposed the etching barrier index (EBI) to describe the difficulty degree of each lattice facet. The raking of EBI will be +c-plane > a-plane > m-plane > −c-plane > (10-1-1) plane > r-plane. Combining the EBI with SEM results, we thoroughly studied the whole etching process. We confirmed that in our research, KOH wet etching on GaN starts from the r-plane instead of the +c-plane or −c-plane, which differs from other studies. We also found that during the high-temperature etching process, there are two etching approaches. In one, the etching begins vertically from the top to the bottom, then horizontally, and finally reversely from the bottom to the top. In the other, etching pits will develop into a hexagonal hole of the sidewall of m-plane.
•Organic/inorganic hybrid nanostructures were grown on sensing chips.•ZnO-based light/gas dual-sensing devices were fabricated.•Incorporation of organic perylene diimide optimized the sensing ...behaviors.•Enhancement of carrier transition was observed inOrganic/inorganic interface.
Organic/inorganic hybrid nanostructures-based dual light-detecting/gas-sensing devices were fabricated. In this research, polycrystalline perylene diimide (PDI) membrane was coated on ZnO nanorods (NRs), functioning as sensing nanocomposites. Multiple material analyses including scanning electron microscope (SEM), energy dispersive spectrometer (EDS), high resolution transmission electron microscopy (HR-TEM), X-ray diffractometer (XRD), Raman spectroscopy, and confocal laser scanning microscopy (CLSM) indicate that organic perylene diimide was successfully deposited on ZnO NRs, forming organic/inorganic membrane on the sensing device. To examine the influence of organic/inorganic hybrid nanostructure on photo-sensing and gas-sensing behaviors, UV light detection and CO gas sensing impulse response were measured. Results reveal that organic/inorganic hybrid nanostructure can effectively enhance UV light and CO gas dual-sensing properties with addition of PDI. The coating of organic PDI on the ZnO NRs not only improves the gas interaction capability and gas-sensing stability but also enhances the UV absorption efficiency. Owing to advantages of low cost, simple fabrication, compact size, and device stability, hybrid PDI/ZnO organic/inorganic light/gas dual-sensing devices are promising for future portable hazardous light and gas sensing applications.
For decades, Moore's Law has been approaching its limits, posing a huge challenge for further downsizing to nanometer dimensions. A promising avenue to replace Moore's Law lies in three-dimensional ...integrated circuits, where Cu-Cu bonding plays a critical role. However, the atomic diffusion rate is notably low at temperatures below 300 °C, resulting in a distinct weak bonding interface, which leads to reliability issues. In this study, a quenching treatment of the Cu film surface was investigated. During the quenching treatment, strain energy was induced due to the variation in thermal expansion coefficients between the Si substrate and the Cu film, resulting in a wrinkled surface morphology on the Cu film. Grain growth was observed at the Cu-Cu bonding interface following bonding at 300 °C for 2 and 4 h. Remarkably, these procedures effectively eliminated the bonding interface.
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