表面電漿是一種電磁波，存在於金屬與介電質的介面，當表面電漿形成時，其電磁場的共振強度對周圍的折射率變化有極高的敏感度，我們可我們藉由量測電磁場的強度或波長變化，來判斷金屬表面的待測物濃度，此方法已廣泛應用在生物感測元件上。 在本研究中，我們利用有機金屬化學氣相沉積法(Metal Organic Chemical Vapor Deposition, MOCVD)成長氮化銦鎵奈米量子井，再以其上的金屬奈米顆粒形成局部性的表面電漿效應，並透過R6G螢光分子所產生的拉曼訊號，來分析此奈米結構在生物感測上的應用潛力。 氮化物半導體具有高折射率、高化學穩定性等優勢。本研究所提出的氮化銦鎵量子井，所產生的光子可作為一種增益介質，補償金屬吸收激發光所造成的能量損失，且金字塔型的奈米結構表面，能增加待測物的吸附面積，配合此獨特的奈米量子井結構，可有效增加表面增益拉曼散射(surface enhanced Raman scattering, SERS)的強度，可偵測最低達10-10M的R6G分子濃度，在單分子偵測上有令人期待的潛力。;Surface plasmon is an electro-magnetic wave, formed at the interface between metal and dielectric. Since the intensity of surface plasmon polaritons (SPP) is extremely sensitive to the change of ambient refractive index, one can determine the concentration of analytes by measuring the shifts of intensity or wavelength of SPP. This method has been widely employed in biosensing technologies. In this study, nano-pyramidal InGaN quantum wells were grown by metal-organic chemical vapor deposition (MOCVD) on Si substrates, with the buffer layer made of ZnO nanorods. Au nanoparticles were then applied on the nanopyramidal surface to induce localized surface plasmon resonance. The Raman signals generated by Rhodamine 6G (R6G) fluorescent dye molecules were evaluated to investigate the biosensing performance of the nano-pyramidal quantum wells. For the applications in biosensing, nitride semiconductors enjoy the advantages of high refractive index, and high chemical stability. Compared to the planar surface, the nano-pyramidal quantum wells are expected to adsorbed more biomolecules because of the increased surface area. Moreover, InGaN quantum well can serve as the gain medium, pumping energy to compensate the ohmic loss in the metal nanoparticles. It is found that the nano-pyramidal quantum wells, together with the Au nanoparticles, are effective in boosting the intensities of surface-enhanced Raman scattering (SERS) signals generated by the R6G molecules.The minimum detectable R6G concentration is 10-10M, showing promising potentials for single molecule detection.
