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  • 學位論文

應用電漿CVD技術及後處理在阻抗與質量式化學感測元件

Application of PECVD and Post Treatment on Resistance and Mass Type Chemical Sensor Devices

指導教授 : 陳克紹
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摘要


化學感測器包含有濕度、pH 值、離子氣體及煙霧等類感測器等,因為科技的進步及生活的便利性,人們開始對生活品質及安全方面的要求也相對的提高,因此一些具有警報跟防護功能的科技產品因而發展出來。例如防災方面有:可燃性氣體及毒性氣體警報器;環境控制方面有:各種氣體偵測器,pH測定器,離子濃度測定器。 本研究主要以應用電漿輔助化學沉積法PECVD (plasma enhanced chemical vapor deposition)技術,及表面接枝聚合來改質無機基材的表面特性,如有機性質、結構組成、親疏水性、官能基特性、及導電性等,來製備濕度/氣體感測器之元件。其主要分為兩部分,在第一部分中使用電漿沉積含聚合醇或矽烷膜及UV光接枝聚合高分子技術製備感濕性元件,第二部分則是以以四甲基錫(tetramethyltin, TMT, Sn(CH3)4)和氧氣(O2 gas)混合為反應單體沉積氧化錫(SnOx)有機薄膜,此有機膜含有過氧化物或自由基,可後續藉由UV光接枝功能性高分子,或是表面塗佈聚乙二醇 PEG (poly ethylene glycol)以改變基材表面的特性。 在第一個部分的研究有兩種方法製作元件,方法一:在梳型電極表面以PECVD 的方式沉積六甲基二矽胺烷HMDSZ (Hexamethyldisilazane)薄膜 ,此表面具有疏水性以及活性基與過氧化基的特性,活性基與過氧化基以利後續接枝聚合,為了提升接枝聚合離子性高分子的量及強度,因此將接枝水溶性單體磺酸化苯乙烯NaSS (Sodium styrenesulfonate)與酚甲醛樹脂(phenol-formaldehyde resin)混合,利用spin coating塗佈於梳型感測電極上,再以UV光照射,製作具有良好抗水溶性與高靈敏的濕度感測器。方法二: 在梳型電極表面以PECVD 的方式聚合異丙醇IPA (isopropanol )薄膜 ,以UV光接枝陰離子水溶性單體丙烯酸AAc (Acrylic acid),製備感濕性薄膜元件。由結果可知以方法一製得之感測元件添加入不同比例的酚甲醛樹脂,其在相對濕度RH 35~95%變化下,呈現約3 orders的感濕阻抗變化(阻抗由106 Ω至103 Ω),而方法二製得之感測元件,其在相對濕度RH 35~95%變化 (阻抗由107 Ω至105 Ω)。 在第二個部分的研究中,在圓形電極上利用電漿聚合及表面複合有機化合物製成有效的半導體型SnOx金屬氧化物一氧化碳感測膜,電漿方法所具有的特點是可製得均勻、低孔隙度的膜而且沈積溫度低等,但是其再現性較差,且對感測器的選擇性較難控制;因此利用光接枝聚合將具有特定的物理或化學性質的單體以化學鍵結方式固定在表面,此方法可透過電漿沈積膜上的過氧化物將有機單體聚合並接枝於無機基材上。研究顯示電漿沉積SnOx膜再以spin coating旋轉塗佈聚乙二醇(PEG) 複合,形成均勻的親水性薄膜,可以在室溫下就可偵測一氧化碳濃度由30 ppm 到 650 ppm.,且對於甲烷、丁烷無明顯的感測性。可取代傳統耗時、高溫偵測選擇性差的改質方式,達到高感測性、高靈敏性、高選擇性的在室溫便可使用的一氧化碳感測元件;再配合檢測實驗用之檢測模組開發,利用蠟燭燃燒來模擬通風不良燃燒不完全的環境進行偵測,建立一套在 CO 濃度≧ 50ppm,閃燈警示,CO 濃度≧100ppm,發出聲音警示,CO 濃度≧200ppm,發出高音量聲警示。應用於工安及環保的氣體感測器之設計,除了靈敏度、選擇性、應答速度之外,還要考慮可攜帶性、耗電量等因素,因此藉著石英晶體振盪器(quartz crystal microbalance,QCM感測器振盪頻率會受表面吸附質量的改變而影響。且具成本低廉、操作容易、原理簡單、應答快速等特性。為了能更具廣泛應用性和可逆性,故可於其無機表面鍵結一層可辨識之感測薄膜,吸附氣體時能造成相對的頻率變化,利用電漿能均勻聚合沉積SnOx膜,以及在無機基材上附著性優良等特點,使無機基材表面有機化,以作為無機物與有機分子的介面層,且可產生過氧化基或活化點,再以旋轉塗布聚乙二醇(PEG) 複合,形成均勻的親水性薄膜,即可用來檢測模擬通風不良燃燒不完全的環境,薄膜能在此環境形成吸附狀態,並且改變QCM震盪頻率,依頻率變化量做為感測器鈴響之訊號。

關鍵字

一氧化碳 感測器 聚乙二醇 電漿

並列摘要


Because of technology improvement and life convenience, people begin to require better life quality and security. When living is getting more convenient, people commence to figure out how to improve life quality; therefore, there are some technical developments of alert and protection products. The plasma deposition and surface grafting polymerization have been used to modify the surface structure and properties of inorganic substrates such as organic nature, structural constitution, hydrophilicity, functional groups, and conductivity. The first part of the fabricating the humidity sensitive layer, the monomeric solution of organic electrolyte NaSS had been spin-coated on the designed electrodes with different patterns, then exposed to UV-light to induce grafting polymerization. The second part of tin oxide (SnOx) organic-like thin films were deposited by plasma enhanced chemical vapor deposition (PECVD) of tetramethyltin (TMT) and O2 gas mixtures at low temperature. The organic-like thin films containing peroxides or free radicals can be subsequently grafted hydrophilic polymer by UV-induced grafting polymerization or spin coating poly ethylene glycol (PEG) on substrate. In this study, humidity sensitive polymer layer containing phenol-formaldehyde resin is prepared by spinning coating on the comb-shape type electrode, then followed by UV-graft polymerization of water soluble monomer which was performed to make water-resistive and the sensitive humidity sensor. In the first part of this study, two types of sensors were developed. The first one was treated with Hexamethyldisilazan (HMDSZ)-plasma and followed by grafting polymerization of NaSS using UV-light and adding different ratio of phenol-formaldehyde resin. This type of sensor has linear response with %RH and high sensitivity (impedance from 106 Ωto 103Ω). The second type of sensor was treated with isopropanol (IPA)-plasma and then grafting polymerization of AAc by UV-light. Also have impedance linear response with %RH, impedance various from 107 Ω to 105Ω. In the second part of this study, surrounding environment, carbon monoxide is often produced as exhaust gas from cars, factory flues, coal, or fuel gas. When an excessive amount of carbon monoxide is inhaled into a human body, it will decrease the oxygen carrying efficiency of hemoglobin. When a human body is exposed to a high concentration of carbon monoxide situation, the cerebrum will lose its normal function and even death may follow. Furthermore, since carbon monoxide possesses the characteristics of lacking color, taste, and stimulus, people cannot detect any danger through their own senses. Therefore, the detection technology of the carbon monoxide detector is particularly important in the present living environment. Post treatment on a new room temperature type gas sensor device based on the organically hybridized plasma deposition of tetramethyltin (TMT) films was developed to detect and distinguish the presence of methane, butane, and carbon monoxide in the test environment. Plasma-deposited thin films were first prepared from TMT and O2 gas mixtures to obtain SnOx thin films at room temperature. Post treatments on the SnOx thin films by (1) spin coating poly ethylene glycol (PEG), or (2) surface grafting acrylamide (AAm) or p-styrenesulfonic acid sodium salt (Nass) were then performed. Higher proportion of TMT in the TMT/O2 mixture tends to increase organic nature of the deposited films and exhibit surface hydrophobic property. Post treatment by spin coating with PEG shows smooth linear response to CO gas, and their sensitivities are not affected by methane or butane gas. The change of sensor resistance can be detected without heating with change in CO concentration from 30 ppm to 650 ppm. Detection experiments with the test modules used to smoldering the development and utilization of a candle burning incomplete combustion of poorly ventilated environment detection CO concentration in the establishment of a ≧ 50ppm, flash warning, CO concentration ≧ 100ppm, sound alerts, CO concentration ≧ 200ppm, given the high volume sound alerts. Used in industrial safety and environmental design in addition to the gas sensor sensitivity, selectivity, response time than should also consider portability, power consumption and other factors, so by quartz crystal microbalance (QCM), QCM sensor is operation easy, simple principles, rapid response and other characteristics, the oscillation frequency will be adsorption of changes in mass. For being widely used and reversible, selective film can be produced on inorganic surface layer of sensor. Tin oxide (SnOx) organic-like thin films were deposited by plasma enhanced chemical vapor deposition (PECVD) of tetramethyltin (TMT) and O2 gas mixtures at low temperature. The organic-like thin films containing peroxides or free radicals can be subsequently hydrophilic polymer PEG by spin coating. The sensor can be used in detecting environment which is smoldering. This film can transform to adsorption state and changes QCM frequency which can be signal to sensor rings.

參考文獻


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