Search for: All records

The use of flashlamp annealing as a low-temperature alternative or supplement to thermal annealing is investigated. Flashlamp annealing and thermal annealing were conducted on 100 nm thick indium tin oxide (ITO) films deposited on glass to compare the properties of films under different annealing methods. The ITO samples had an average initial sheet resistance of 50 Ω/sq. After flashlamp annealing, the sheet resistance was reduced to 33 Ω/sq only, while by thermal annealing at 210 °C for 30 min, a sheet resistance of 29 Ω/sq was achieved. Using a combination of flashlamp annealing and thermal annealing at 155 °C for 5 min, a sheet resistance of 29 Ω/sq was achieved. X-ray diffraction analysis confirmed that flashlamp annealing can be used to crystallize ITO. Flashlamp annealing allows for low-temperature crystallization of ITO on a time scale of 1–3 min. Through electrical and optical characterizations, it was determined that flashlamp annealing can achieve similar electrical and optical properties as thermal annealing. Flashlamp offers the method of low-temperature annealing, which is particularly suitable for temperature sensitive substrates.

 

Silver thin films have wide-ranging applications in optical coatings and optoelectronic devices. However, their poor wettability to substrates such as glass often leads to an island growth mode, known as the Volmer–Weber mode. This study demonstrates a method that utilizes a low-energy ion beam (IB) treatment in conjunction with magnetron sputtering to fabricate continuous silver films as thin as 6 nm. A single-beam ion source generates low-energy soft ions to establish a nominal 1 nm seed silver layer, which significantly enhances the wettability of the subsequently deposited silver films, resulting in a continuous film of approximately 6 nm with a resistivity as low as 11.4µΩ.cm. The transmittance spectra of these films were found to be comparable to simulated results, and the standard 100-grid tape test showed a marked improvement in adhesion to glass compared to silver films sputter-deposited without the IB treatment. High-resolution scanning electron microscopy images of the early growth stage indicate that the IB treatment promotes nucleation, while films without the IB treatment tend to form isolated islands. X-ray diffraction patterns indicate that the (111) crystallization is suppressed by the soft IB treatment, while growth of large crystals with (200) orientation is strengthened. This method is a promising approach for the fabrication of silver thin films with improved properties for use in optical coatings and optoelectronics.

 

A single beam plasma source was used to deposit hydrogenated amorphous carbon (a-C:H) coatings at room temperature. Using methane source gas, a-C:H coatings were deposited at different radio frequency (RF) power to fabricate transparent and durable coatings. The film deposition rate was almost linearly proportional to the ion source power. Hydrogenated amorphous carbon films of ~100 nm thickness appeared to be highly transparent from UV to the infrared range with a transmittance of ~90% and optical bandgap of ~3.7 eV. The coatings also possess desirable mechanical properties with Young’s modulus of ~78 GPa and density of ~1.9 g/cm3. The combined material properties of high transmittance and high durability make the ion-source-deposited a-C:H coatings attractive for many applications. 

A single-beam plasma source was developed and used to deposit hydrogenated amorphous carbon (a-C:H) thin films at room temperature. The plasma source was excited by a combined radio frequency and direct current power, which resulted in tunable ion energy over a wide range. The plasma source could effectively dissociate the source hydrocarbon gas and simultaneously emit an ion beam to interact with the deposited film. Using this plasma source and a mixture of argon and C2H2 gas, a-C:H films were deposited at a rate of ∼26 nm/min. The resulting a-C:H film of 1.2 µm thick was still highly transparent with a transmittance of over 90% in the infrared range and an optical bandgap of 2.04 eV. Young’s modulus of the a-C:H film was ∼80 GPa. The combination of the low-temperature high-rate deposition of transparent a-C:H films with moderately high Young’s modulus makes the single-beam plasma source attractive for many coatings applications, especially in which heat-sensitive and soft materials are involved. The single-beam plasma source can be configured into a linear structure, which could be used for large-area coatings.

 

Bistable liquid crystal (LC) shutters have attracted much interest due to their low energy consumption and fast response time. In this paper, we demonstrate an electrically tunable/switchable biostable LC light shutter in biological optics through a three–step easy–assembly, inexpensive, multi–channel shutter. The liquid crystal exhibits tunable transparency (100% to 10% compared to the initial light intensity) under different voltages (0 V to 90 V), indicating its tunable potential. By using biomedical images, the response time, resolution, and light intensity changes of the LC under different voltages in three common fluorescence wavelengths are displayed intuitively. Particularly, the shutter’s performance in tumor images under the near–infrared band shows its application potential in biomedical imaging fields. 

Abstract A single-beam ion source was developed and used in combination with magnetron sputtering to modulate the film microstructure. The ion source emits a single beam of ions that interact with the deposited film and simultaneously enhances the magnetron discharge. The magnetron voltage can be adjusted over a wide range, from approximately 240 to 130 V, as the voltage of the ion source varies from 0 to 150 V, while the magnetron current increases accordingly. The low-voltage high-current magnetron discharge enables a ‘soft sputtering mode’, which is beneficial for thin-film growth. Indium tin oxide (ITO) thin films were deposited at room temperature using a combined single-beam ion source and magnetron sputtering. The ion beam resulted in the formation of polycrystalline ITO thin films with significantly reduced resistivity and surface roughness. Single-beam ion-source-enhanced magnetron sputtering has many potential applications in which low-temperature growth of thin films is required, such as coatings for organic solar cells.