難熔電漿子材料的開發與應用:氮化鉿電漿子晶體實現全彩顯色

Abstract

無背光彩色顯示器一直是熱門研究主題，其中一種常見的手段是利用奈米結構的電漿子特性，便能做到照光即顯示不同顏色的效果。此外奈米結構的無背光彩色顯示器有望在光電產業上的互補式金屬氧化物半導體元件(Complementary metal-oxide semiconductor device)有著良好的相容性。過去的無背光彩色顯示器1多利用金2、銀3、鋁4 等傳統金屬的奈米結構產生表面電漿共振(Surface plasmon resonance, SPR)或局域電漿共振(Localized surface plasmon resonance, LSPR)，然而這些傳統金屬各別有造價高、低熔點、化學性質不穩定等問題，因此材料便需要新的替換選擇，其中過渡金屬氮化物(Transition metal nitride, TMN)便具備價格便宜、高熔點、化學性質穩定、高硬度等優點。 本實驗室長期致力於過渡金屬氮化物的研究，我們發現大部分文獻皆在探討氮化鈦(Titanium nitride, TiN)以及氮化鋯(Zirconium nitride, ZrN)奈米結構的電漿子特性與應用，但對於氮化鉿(Hafnium nitride, HfN)的研究相當稀少。本篇研究即是利用氮化鉿(Hafnium nitride, HfN)具有高介電常數近零(Epsilon near zero, ENZ)5 (~3.1 eV)的電漿子特性，並控制不同奈米結構來改變表面電漿子共振的波段，進而做到不同波段的吸收，最後達到控制顏色的效果，做出具有全彩顯色功能的無背光彩色顯示器。而HfN除了有上述特性以外，它的造價也相對便宜，還具由難熔性質(Refractory)，熔點高達三千多度(Tm~3583˚C)、高化學穩定性(Chemical stability)、良好的機械特性(Mechanical hardness)6, 7 8，這些條件使得氮化鉿有望比傳統金屬(例如:金、銀、鋁……)在苛刻的實驗操作具有穩定的光學特性。 本文研究射頻磁控濺鍍成長的氮化鉿薄膜的複數介電常數表現，並利用有限時域差分(Finite-difference time-domain, FDTD)模擬奈米圓盤結構以及光柵結構，控制表面電漿子共振波段(450 nm~850 nm)已達到改變顏色的效果，最終實現氮化鉿無背光彩色顯示器及利用光柵結構的偏振選擇性做出相關應用。此外本文也討論氮化鉿奈米結構與傳統金屬奈米結構在溫度穩定性、環境穩定性的比較。

Backlight-free displays have been a hot research topic for many years. One of the common approaches is to use the plasmonic properties of nanostructures to display different colors. The nanostructure backlight-free displays are expected to be compatible with complementary metal-oxide semiconductor (CMOS) devices in the optoelectronics industry. In the past, the backlight-free displays mostly used the nanostructures of traditional metals such as gold, silver, and aluminum. However, there are some problems like high cost, low melting point, and unstable chemical properties. Therefore, we need the alternative plasmonic materials. Transition metal nitrides (TMN) have the advantages of low price, high melting point, stable chemical properties, high hardness, etc. Our laboratory has been devoted to the research of transition metal nitrides for a long time. We found that most of the works of literature have discussed the plasmonic properties and applications of titanium nitride (TiN) and zirconium nitride (ZrN) nanostructures, but hafnium nitride (HfN) is seldom to be studied. The high epsilon near zero(ENZ) (~3.1 eV) of HfN makes it a good candidate for a color filter. By changing the different geometry parameters of the nanostructure (period, height, and radius), we can modulate the absorption peak to demonstrate different colors, which achieve a backlight-free display. Also, HfN, which is relatively inexpensive to manufacture, has refractory properties, a melting point as high as 3,000 ˚C (Tm~3583˚C), high chemical stability and well mechanical hardness. These properties make HfN has more stable optical properties than traditional metals (e.g., gold, silver, aluminum) in harsh experimental operations. This thesis studied the complex refractive index performance of HfN films grown by RF magnetron sputtering. And we simulated nanodisk and nanograting array structures using the finite-time domain-difference (FDTD) method to generate the colors by tuning the wavelength of surface plasmonic resonance(400 nm ~ 850 nm). In this work, we successfully realized the HfN backlight-free displays, which can be controlled from blue to red on the subwavelength scale. And the application of the polarized-selectively of the grating structure. In addition, we also discussed the comparison of the high thermal and environmental stabilities between HfN nanostructure and traditional metal.