臺灣博碩士論文加值系統

本論文之研究是以奈米碳管為基礎所建立之氣體感測器、溼度計和溫度計。我
們使用p-type 的矽晶片做為元件的基板，在這基板上熱氧化的方式成長二氧化矽之
絕緣層。我們的感測器包含了利用電泳方式讓奈米碳管交互連結的指插狀圖形電
極、自製的熱電偶器以及微型加熱器。整個實驗是在一利用膠帶封閉的塑膠容器內，
且內部放有乾燥劑以控制溼度的變化。另外，為了正確的讀出溼度值也放入商用型
的溼度計在容器內。從實驗的結論來看，當溼度改變時，以奈米碳管為感測材料的
元件其電阻值會明顯地變化。而根據吸附在碳管上的水分子多寡造成電阻值的變化
程度，可了解到空氣內所含有的水分子含量。此外，我們也量測以奈米碳管為基礎
的元件電阻值對於溫度的變化程度。而實驗結果指出，多壁奈米碳管對於溫度的反
應是金屬性的特性。另外也設計了三極式的特構，其三極式場效電晶體結構的閘極
電壓則是為了嘗試增加對溼度靈敏度而設計的，有趣的是多壁奈米碳管的電阻值並
不會隨著閘極電壓的改變而有所增減，這項發現也直接地証實了多壁奈米碳管之電
阻可以由水分子吸收於二氧化矽/碳管界面上之截體變化率而明顯的改變。
從最後的實驗結論顯示，可利用元件的電阻值變化對環境的溼度和溫度做偵
測，也使得多壁奈米碳管可成為具未來發展性的環境感測材料。

Fabrication of gas sensor, hygrometer and thermometer which based on carbon
nanotubes (CNTs) is demonstrated. The thermally grown silicon dioxide (SiO2) on the
p-type silicon wafer was used as the substrate. The sensor contains metal electrodes
which were designed as the interdigitated pattern and the CNTs were interlinked with the
electrodes by dielectrophoresis (DEP) method. An integrated thermocouple as
temperature detector, and a micro heater was also fabricated. The experiments were
performed in a plastic desiccator which contains the exsiccative and sealed with sellotape.
A commercial hygrometer was placed in the desiccator to read out the humidity value
when the humidity percentage varying. The results indicate that this two-terminal device
has its electric resistance changes when varying the humidity. According to the water
molecules adsorbed on CNTs to cause their resistance varies, we can define the capacity
of water molecules holding at the air. In addition, we also measured the device resistance
variation versus temperatures. The response of metallic behavior represents that
multiwalled carbon nanotubes (MWCNTs) are metal-like. We also demonstrated a
three-terminal FET structure attempt to improve the sensitivity by back gate voltage. It is
interesting that the electric resistance of MWCNTs is independence to the gate voltage.
This discovery explains that the MWCNT responds to the humidity based on carrier traps
form by the SiO2/CNT interface.
The final results show that the environmental humidity and temperature can be
detected by the device’s electric resistance, and imply that MWCNTs can be a promising
material for environment monitoring.

ENGLISH ABSTRACT I
CHINESE ABSTRACT II
ACKNOWLEDGEMENTS III
TABLES OF CONTEXTS IV
LIST OF FIGURES VI
LIST OF TABLES XI
CHAPTER
I INTRODUCTION 1
1.1 Scope of this thesis 1
1.2Carbon nanotube properties 1
1.2.1Physics properties of carbon nanotube 1
1.2.2Electric properties of carbon nanotubes 7
1.3Commercial devices of gas sensor, hygrometer, and thermometer 9
1.3.1Principle of commercial gas sensor 10
1.3.2Principle of commercial relative humidity sensor 19
1.3.3Principle of commercial thermometer 24
II DESIGN AND FABRICATION OF MWCNT INTEGRATED
GAS SENSOR 29
2.1Design concept of the MWCNT integrated gas sensor 29
2.2Fabrication of the MWCNT integrated gas sensor 29
2.3Measurement of the MWCNT integrated gas sensor 43
2.4Discussion of the MWCNT integrated gas sensor 48
III DESIGN AND FABRICATION OF MWCNT INTEGRATED
HYGROMETER 50
3.1Design concept of the MWCNT integrated hygrometer 50
3.2Fabrication of the MWCNT integrated hygrometer 50
3.3Measurement of the MWCNT integrated hygrometer 50
3.4Discussion of the MWCNT integrated hygrometer 60
IV DESIGN AND FABRICATION OF MWCNT INTEGRATED
THERMOMETER 61
4.1Design concept of the MWCNT integrated thermometer 61
4.2Fabrication of the MWCNT integrated thermometer 61
4.3Measurement of the MWCNT integrated thermometer 72
4.4Discussion of the MWCNT integrated thermometer 75
V CONCLUSION AND FUTURE WORKS 75
REFERENCES
APPENDICES
1. Measurement instrument.
2. Control software for data acquisition
3. Publication list

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