紫外光雷射燒結奈米氧化鎳薄膜之特性分析與應用

Abstract

熱透鏡效應是因不可預期的透鏡加熱變形而導致折射率改變、焦點位移的現象。造成異常的加溫之原因主要是光學元件表面沾黏加工碎屑或是劣質光學元件導致熱能在透鏡中累積。因此，在本研究中運用氧化鎳薄膜熱敏電阻來達到監控球形透鏡中心溫度的目的。感測薄膜透過氣溶膠噴印技術可以精準且有效率的製作於曲面之上。 為了達到高效率的小批量生產，感測器的燒結利用355奈米波長紫外光雷射並搭配噴印技術進而達到縮減工序以及降低製程時間的效果。相較於先前研究常見的烘箱燒結製程，紫外光雷射不只大幅度的增加電性並且將單一熱敏電阻的燒結時間從一小時降至一秒左右。實驗結果顯示最佳雷射燒結參數將氧化鎳熱敏電阻從烘箱燒結的電阻106.8 MΩ 降低到了 6.15 MΩ，使得氧化鎳熱敏電阻可以在常溫之下穩定的操作。本研究中以電性、表面形貌和X光繞射分析(XRD)，探討了紫外光雷射對於氧化鎳燒結影響。當能量過高時，發現紫外光雷射的高能量吸收會產生薄膜裂縫並降低電阻。XDR分析中顯示，不管是晶粒大小或是晶面距離都顯示紫外光雷射在實驗範圍內並沒有造成薄膜的再結晶，且有應力累積的現象。燒結後薄膜表面的裂縫是因為區域不均勻的收縮應變所導致。 熱敏電阻應用於球面鏡的結果顯示，感測器擁有高敏感度，穩定，可重複性，且沒有出現遲滯的現象。將測量到的熱敏電阻溫度利用熱傳公式計算鏡面中心溫度與實際使用熱像儀所偵測到的鏡面中心溫度進行誤差分析，計算的中心溫度和測量溫度的最大差異只有3.7%。證明本研究所提出之方法可用於球面鏡中心溫度監測。

Thermal lens effect occurs due to the unexpected deformation of lens caused by laser abnormal heating, which has an impact on refractive index of lens. Usually, optic contaminations or bad quality of lens are two main reasons that cause abnormal heating and eventually lead to focal plane shifting. Therefore, a novel method, printed nanoparticle NiO thin film thermistors with Radial heat flow method, was applied for temperature detection of lens in this study. The thin film thermistors were printed by an aerosol jet printer, which is capable of fabricating thin films on the curve substrate via air stream. To approach high efficiency fabricating thin film thermistors in small batch sizes, the printed NiO nanoparticle thin films were sintered by using a 355 nm wavelength ultraviolet (UV) laser; this novel fabrication method reduced several steps of the conventional manufacturing process of the thermistor. Compared with furnace heat treatments of the NiO thermistor in previous studies, the UV laser sintering not only significantly improved the electrical properties but decreased the treatment time from an hour to a second. Since the resistance declined, the thermistor has been operated at an ambient temperature, which provides ready measurement. The resistance, morphology and XRD patterns of the thin films were analyzed for evaluating the effect of the laser treatment. Due to the laser-sintering parameters, namely, 2 W, 150 mm/s, 90 kHz, and a B value of 4683 K, the resistance has been reduced from 106.8 MΩ to 6.15 MΩ at 100 °C. For NiO nanoparticles, UV laser has higher absorption energy than that of other wavelength lasers, when excess laser output was applied to the NiO thin film, cracks were observed on the surface. It was found that the crystal plane distances were not affected by recrystallization, but the cracks were based on the XRD analysis. Based on the analysis, there were obvious regional compressive stains before the appearance of cracks, and the uneven shrinking strains caused the cracks on the surface as energy irradiation increased. According to the performance of the thermistors on lenses, the detection properties of NiO thin films were sensitive, stable, repeatable and without any hysteretic effects. Therefore, the method of thermistor and thermal conduction equation was feasible for temperature detection of focal lenses. The deviation between the detected temperatures and calculated temperatures from the thermal conduction equation were negligible. According to the results of calculated temperature, the deviations from thermal equation were able to be minimized by minifying the volume difference between lens and mathematical model and considering the effect of various radius of curvature on heat transfer rates