半導體碘化鉛薄膜在單結晶銠電極上的研究; Synthesis and Characterization of Lead Iodide Semiconducting Film Deposited on Rh(100) and Rh(111) single crystal electrodes.

Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/5898

Title:	半導體碘化鉛薄膜在單結晶銠電極上的研究;Synthesis and Characterization of Lead Iodide Semiconducting Film Deposited on Rh(100) and Rh(111) single crystal electrodes.
Authors:	楊家慧;Chia-Huei Yang
Contributors:	化學研究所
Keywords:	碘化鉛;STM;Scanning Tunneling Microscopy;Lead Iodide
Date:	2002-07-08
Issue Date:	2009-09-22 10:09:52 (UTC+8)
Publisher:	國立中央大學圖書館
Abstract:	本論文主旨在研究經碘修飾後銠(Rh)單結晶電極上碘化鉛(Lead Iodide)薄膜的結構及未經碘修飾之銠單晶電極吸附碘化鉛粒子的大小，並利用掃描式電子穿隧顯微鏡(Scanning Tunneling Microscpoe，STM)、X-射線光電子光譜(X-ray Photoelectron Spectroscopy，XPS)、紫外光-可見光吸收光譜(UV-Vis Absorption Spectrophotometer)及螢光光譜，檢測碘化鉛薄膜的原子結構和光學性質。結果顯示，先行吸附的碘原子層在銠（100）及（111）上分別形成(√2 × √2) R45°和(√3 × √3) R30°的高度規則結構。若以經碘修飾之銠電極作為吸附碘化鉛的載體則可得到平整、缺陷少的碘化鉛薄膜，其原子排列為六方最密堆積。但是未經碘修飾的銠電極在水及氰甲烷(acetonitrile)溶液中吸附碘化鉛，碘化鉛會以粒子的形式吸附而非薄膜的形式，我們利用STM觀察碘化鉛粒子的大小分別為1.5、3.1和5.8 nm，而這些奈米粒子亦造成在可見光譜中287(4.32 eV)、364(3.4 eV)和409(3.0 eV) nm的吸收特色，反映出半導體能階隨著材料縮小而明顯的增加。另外，碘化鉛塊體（bulk）時的螢光釋放是位於496.8 nm，但是碘化鉛粒子之螢光波長則是在414和478 nm釋放，若在銠電極 I 上形成碘化鉛多層薄膜時，則放出445 nm的螢光，不論是粒子或薄膜都有明顯的藍位移(blue shift)現象。此外，碘化鉛薄膜的螢光釋放，會隨著吸附時間的增加螢光強度也隨之增強，但是波長卻沒有位移的現象，也就是說薄膜的厚度並沒有增加，顯示出碘化鉛薄膜的成長方式可能為不連續的狀態。我們推測另一種可能，為電極上的碘化鉛膜厚也受限制的緣故。由Pb2+的兩個還原峰特色和總電荷量可推測吸附時間為1分鐘時，碘化鉛薄膜為多層吸附，但膜厚應小於50層。最後，在溼度約為60%的大氣環境中，碘化鉛薄膜的表面處於一水合狀態下，本篇實驗也利用STM的探針與碘化鉛之間的偏壓，來對碘化鉛薄膜作有效的沉積與蝕刻。 Adsorption of iodine atoms from a vapor phase onto an annealed Rh(100) single crystal produced either a well-ordered monolayer or multiple layers iodine, depending on the dosing levels. High-quality scanning tunneling microscopy (STM) atomic resolutions of these iodine adlayers were achieved, rendering the characterization of a (√2 × √2)R45° - I structure for the monolayer case and two different structures for the multiple layer cases. These iodine adlayers served as the substrates onto which PbI2 films were deposited from aqueous solutions of Pb(NO3)2 with KI mixed in the presence of excess amount of acetonitrile. X-ray photoelectron spectroscopy results also indicate the presence of stoichiometric amounts of Pb2+ and I- ions at the surface of Rh(100). STM imaging of these PbI2 films in air revealed a hexagonal array with a lattice constant of 0.45 nm, consistent with the ideal value of PbI2 crystal. The strong van der Waals interactions between the iodine overlayer and one of the iodide layers of PbI2 are responsible for the deposition of PbI2 on the surface. STM tentatively discerned the atomic arrangements of the uppermost iodide layer of PbI2.
Appears in Collections:	[Graduate Institute of Chemistry] Electronic Thesis & Dissertation

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