表面增强红外吸收（SEIRA）增强和光谱质量对底层衬底选择的依赖性：更深入地研究物理气相沉积（PVD）制备的银（Ag）薄膜。

Dependence of surface-enhanced infrared absorption (SEIRA) enhancement and spectral quality on the choice of underlying substrate: a closer look at silver (Ag) films prepared by physical vapor deposition (PVD).

机构信息

Dept. of Chemistry and Physics and USC NanoCenter, University of South Carolina Aiken, Aiken, South Carolina 29801, USA.

出版信息

Appl Spectrosc. 2011 Mar;65(3):272-83. doi: 10.1366/10-06176.

DOI:10.1366/10-06176

PMID:21352647

Abstract

Silver (Ag) films of varying thickness were simultaneously deposited using physical vapor deposition (PVD) onto six infrared (IR) substrates (BaF(2), CaF(2), Ge, AMTIR, KRS-5, and ZnSe) in order to correlate the morphology of the deposited film with optimal SEIRA response and spectral band symmetry and quality. Significant differences were observed in the surface morphology of the deposited silver films, the degree of enhancement provided, and the spectral appearance of para-nitrobenzoic acid (PNBA) cast films for each silver-coated substrate. These differences were attributed to each substrate's chemical properties, which dictate the morphology of the Ag film and ultimately determine the spectral appearance of the adsorbed analyte and the magnitude of SEIRA enhancement. Routine SEIRA enhancement factors (EFs) for all substrates were between 5 and 150. For single-step Ag depositions, the following ranking identifies the greatest SEIRA enhancement factor and the maximum absorption of the 1345 cm(-1) spectral marker of PNBA at the optimal silver thickness for each substrate: BaF(2) (EF = 85 ± 19, 0.059 A, 10 nm Ag) > CaF(2) (EF = 75 ± 30, 0.052 A, 10 nm Ag) > Ge (EF = 45 ± 8, 0.019 A, 5 nm Ag) > AMTIR (EF = 38 ± 8, 0.024 A, 15 nm Ag) > KRS-5 (EF = 24 ± 1, 0.015 A, 12 nm Ag) > ZnSe (EF = 9 ± 5, 0.008 A, 8 nm Ag). A two-step deposition provides 59% larger EFs than single-step depositions of Ag on CaF(2). A maximum EF of 147 was calculated for a cast film of PNBA (surface coverage = 341 ng/cm(2)) on a 10 nm two-step Ag film on CaF(2) (0.102 A, 1345 cm(-1) symmetric NO(2) stretching band). The morphology of the two-step Ag film has smaller particles and greater particle density than the single-step Ag film.

摘要

为了将沉积膜的形态与最佳表面增强拉曼散射（SEIRA）响应和光谱带对称性和质量相关联，使用物理气相沉积（PVD）同时在六个红外（IR）衬底（BaF(2)、CaF(2)、Ge、AMTIR、KRS-5 和 ZnSe）上沉积不同厚度的银（Ag）薄膜。观察到沉积银薄膜的表面形态、提供的增强程度以及对硝基苯甲酸（PNBA）铸膜的光谱外观存在显著差异每个涂银基底。这些差异归因于每个基底的化学性质，这些性质决定了 Ag 薄膜的形态，最终决定了吸附分析物的光谱外观和 SEIRA 增强的幅度。所有基底的常规 SEIRA 增强因子（EF）均在 5 到 150 之间。对于单步 Ag 沉积，以下排名确定了最大 SEIRA 增强因子和 PNBA 的 1345 cm(-1)光谱标记的最大吸收在每个基底的最佳银厚度：BaF(2)（EF = 85 ± 19，0.059 A，10 nm Ag）> CaF(2)（EF = 75 ± 30，0.052 A，10 nm Ag）> Ge（EF = 45 ± 8，0.019 A，5 nm Ag）> AMTIR（EF = 38 ± 8，0.024 A，15 nm Ag）> KRS-5（EF = 24 ± 1，0.015 A，12 nm Ag）> ZnSe（EF = 9 ± 5，0.008 A，8 nm Ag）。两步沉积提供的 EF 比 CaF(2)上的单步 Ag 沉积大 59%。通过两步 Ag 沉积在 CaF(2)上沉积 10nm 的 Ag 薄膜（表面覆盖率 = 341ng/cm(2)），计算得到 PNBA 铸膜的最大 EF 为 147（EF = 147，0.102 A，1345 cm(-1)对称 NO(2)伸缩带）。两步 Ag 薄膜的形态比单步 Ag 薄膜具有更小的颗粒和更大的颗粒密度。