A review is provided, which first considers low-temperature diffusion bonding with silver nanomaterials as filler materials via thermal sintering for microelectronic applications, and then other recent innovations in low-temperature joining are discussed. The theoretical background and transition of applications from micro to nanoparticle (NP) pastes based on joining using silver filler materials and nanojoining mechanisms are elucidated. The mechanical and electrical properties of sintered silver nanomaterial joints at low temperatures are discussed in terms of the key influencing factors, such as porosity and coverage of substrates, parameters for the sintering processes, and the size and shape of nanomaterials. Further, the use of sintered silver nanomaterials for printable electronics and as robust surface-enhanced Raman spectroscopy substrates by exploiting their optical properties is also considered. Other low-temperature nanojoining strategies such as optical welding of silver nanowires (NWs) throu...

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Joining of Silver Nanomaterials at Low Temperatures: Processes, Properties, and Applications

We present a method for the sintering of silver (Ag) nanoparticle thin films by millisecond pulsed laser irradiation. The microstructure of sintered thin films and sintering behaviors of nanoparticles were systematically investigated in this paper. Absorption spectra of sintered thin films showed blue-shifted surface plasmon resonances (SPR) from 500 nm to 480 nm and red-shifted from 480 nm to 550 nm when laser power was varied from 100 W to 140 W and from 140 W to 200 W, respectively. This indicates a new technique to control light absorption through joining nanoparticles with laser sintering. According to theoretical calculations based on a heat diffusion model, the melting temperature of these Ag nanoparticles was estimated to be 440 °C during laser irradiation.

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Laser sintering of silver nanoparticle thin films: microstructure and optical properties

Nanojoining, a burgeoning research area, becomes a key manufacturing of complicated nanodevices with functional prefabricated components. In this work, various nanojoining methods are first reviewed. For nanojoining of Ag/Au nanoparticles, three methods are investigated comparatively. Thermal annealing shows a two-step solid state diffusion mechanism. Laser annealing by millisecond pulses displays the thermal activated solid state diffusion. Meanwhile, two effects have been identified in femtosecond laser irradiation with different laser intensities: photofragmentation at rather high intensity (∼1014 W/cm2) and nanojoining at low intensity (∼1010 W/cm2). The photofragmentation forms a large number of tiny nanoparticles with an average size of 10 nm. Control over irradiation conditions at intensities near 1010 W/cm2 results in nanojoining of most of the nanoparticles. This nanojoining is obtained through a nonthermal melting and a surface fusion welding. Joined Au nanoparticles are expected to have numerou...

https://uwaterloo.ca/centre-advanced-materials-joining/sites/ca.centre-advanced-materials-joining/files/uploads/files/jla042001-hu.pdf

Femtosecond laser welded nanostructures and plasmonic devices

A comparative study of carbon bonding states and Raman spectra is reported for amorphous diamondlike carbon films deposited using 120fs and 30ns pulsed laser ablation of graphite. The presence of sp1 chains in femtosecond carbon films is confirmed by the appearance of a broad excitation band at 2000–2200cm−1 in UV-Raman spectra. Analysis of Raman spectra indicates that the concentrations of sp1-, sp2-, and sp3-bonded carbon are ≈6%, ≈43%, and ≈51%, respectively, in carbon films prepared by femtosecond laser ablation. Using surface enhanced Raman spectroscopy, specific vibrational frequencies associated with polycumulene, polyyne, and trans-polyacetylene chains have been identified. The present study provides further insight into the composition and structure of tetrahedral carbon films containing both sp2 clusters and sp1 chains.

Spectroscopic Characterization of Carbon Chains in Nanostructured Tetrahedral Carbon Films Synthesized by Femtosecond Pulsed Laser Deposition

Fundamentals of femtosecond laser pulse and nanoparticles are analyzed by a two-temperature model. Ultrafast surface melting, surface nanoengineering and shock wave impact are evident in the surface of graphite by femtosecond irradiation. The interaction between femtosecond laser pulses and Au/Ag nanoparticles has been investigated. Two effects are identified at different intensities: photofragmentation at rather high intensity (~10 14 W/cm 2 ), nanojoining at low intensity (~10 10 W/cm 2 ). Photofragmentation forms a large number of tiny nanoparticles with an average size of tens of nanometers. Control over irradiation conditions at intensities near 10 10 W/cm 2 results in nanojoining of most of the nanoparticles. This nanojoining is obtained in both liquid solution and in solid state thin films assembled from nanoparticles. Nanojoining mechanism is further studied by joining Ag nanoparticles encapsulated by a polymer shell. Nonthermal melting is investigated. Nanojoined Au nanoparticles are expected to have numerous applications, such as probes for surface enhance Raman spectroscopy.

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Femtosecond Laser-Induced Nanowelding: Fundamentals and Applications

Metal nanostructures show great applications in chemical sensing, biomedical detection, optical-thermal therapy, and optical communications because of their electromagnetic field enhancement properties at the visible and the near-field infrared wavelengths. Such strong optical field enhancement induced by the localized surface plasmon resonance is dependent on the configurations and the sizes of the metal nanoparticles. We presented a numerical investigation of the plasmonic properties of the individually welded silver nanoparticles fabricated by nanojoining technique. It shows that the field enhancement factor in welded silver nanostructures is much larger than in separated silver nanoparticles. The size dependent localized surface plasmon resonance spectra and the polarization sensitivity property of such configurations are also discussed.

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Plasmonic Properties of Welded Metal Nanoparticles

The invention discloses a silicon-based OLED pixel circuit and a method for compensating the change of the electrical properties of an OLED. The silicon-based OLED pixel circuit is composed of four metal-oxide-semiconductor field-effect tubes, one storage capacitor and one organic light-emitting diode. For the silicon-based OLED pixel circuit and the method for compensating the change of the electrical properties of the OLED, the organic light-emitting diode is placed at the drain electrode of a driving tube, the driving tube is enabled to work at the saturation region, so that the working current of the driving tube is irrelevant to the voltage of the drain electrode of the driving tube, therefore, the influences of the change of the electrical properties caused by ageing of the organic light-emitting diode on the working current of the organic light-emitting diode are eliminated, the problem that the luminance of a silicon-based OLED microdisplay decreases is improved, and the display quality of the microdisplay is improved.

Silicon-based OLED pixel circuit and method for compensating change of electrical properties of OLED

The invention discloses a silicon-based OLED (Organic Light Emitting Diode) pixel circuit and a method for compensating driving tube threshold voltage drift. The silicon-based OLED pixel circuit consists of 6 metal-oxide-semiconductor field effect transistors, 1 storage capacitor and 1 organic light emitting diode. Through the silicon-based OLED pixel circuit and the method for compensating the driving tube threshold voltage drift, in the threshold voltage compensating stage, the threshold voltage and the data voltage of a driving tube are stored in the storage capacitor, and the driving tubeworks in a saturation region, so that the working current of the organic light emitting diode is independent of the threshold voltage of the driving tube, and influences of the threshold voltage driftof the driving tube on the working current of the organic light emitting diode are eliminated, the brightness uniformity of a silicon-based OLED microdisplay is improved, and the display effect of the microdisplay is improved.

Li Chen

Papers

Plasmonic Properties of Welded Metal Nanoparticles

Silicon-based OLED pixel circuit and method for compensating change of electrical properties of OLED

Silicon-based OLED (Organic Light Emitting Diode) pixel circuit and method for compensating driving tube threshold voltage drift