Femtosecond激光结合去湿法制备高敏感均匀SERS基底：增强因子达9.2×107

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本文报道了一种利用飞秒激光结合退火技术制备高灵敏度和均匀性的表面增强拉曼散射(SERS)基底的简单、经济且可重复的方法。研究人员在硅片上通过飞秒激光微加工出精细结构，然后覆盖一层金膜。经过退火处理后，光的捕获效应使得表面的电场增强显著提升。实验结果显示，5纳米厚的金膜覆盖下，该SERS基底的增强因子高达9.2×10^7，表明其具有极高的敏感性。这种新型SERS基底的关键在于飞秒激光的微纳加工技术，它能够精确控制材料的微观形貌，从而优化光学性能。通过光陷阱效应，光线在微结构表面停留的时间增加，增强了局部电磁场，从而增强了对分子间极化振动的放大效果。此外，论文还强调了该基底的均匀性，通过拉曼映射显示出信号的均一性，最显著的强度变化仅达到6%，这在长时间的化学稳定性测试下依然保持，确保了长期的稳定性能。飞秒激光与退火相结合的优势在于其工艺的简便性和一致性，这对于大规模生产和集成在微芯片中的SERS功能具有重要的意义。这项研究为微电子设备集成高效SERS传感器提供了新的途径，有望推动SERS技术在生物分析、环境监测和材料科学等领域中的广泛应用。这篇论文介绍了一种创新的SERS基底制备方法，它不仅提高了光谱信号的增强能力，而且保证了信号的均匀分布，这对于提高SERS的信噪比和检测精度至关重要。这一研究成果对于推进SERS技术的实用化和规模化应用具有重要意义。

Highly sensitive and homogeneous SERS substrate

fabricated by a femtosecond laser combined

with dewetting

Xudong Tan (谭旭东), Lan Jiang (姜澜), Jie Hu (胡洁)*, Pengjun Liu (刘鹏军),

Andong Wang (王安东), and Yong Lu (芦勇)

Laser Micro/Nano Fabrication Laboratory, School of Mechanical Engineering,

Beijing Institute of Technology, Beijing 100081, China

*Corresponding author: jiehu2@bit.edu.cn

Received June 16, 2015; accepted September 10, 2015; posted online October 5, 2015

We report a simple, cost-effective and repeatable method for fabricating a large area and uniform substrate for

surface-enhanced Raman scattering (SERS). The silicon, micromachined by a femtosecond laser, is coated with

gold film and then treated through the dewetting process. The morphology shows a higher electric field enhance-

ment due to light trapping. The enhancement factor of the SERS substrate is 9.2 × 10

with a 5 nm-thick film

coated. Moreover, it also exhibits a uniform signal through Raman mapping and chemical stability with the

greatest intensity deviation of 6% after a month. The proposed technique provides an opportunity to equip

microchips with the SERS capabilities of high sensitivity, chemical stability, and homogeneous signals.

OCIS codes: 240.6695, 140.7090.

doi: 10.3788/COL201513.111401.

Since its discovery in 1974 by Fleischmann et al.,

surface-enhanced Raman scattering (SERS) has been ex-

tensively researched in chemistry, biology, and materials

sciences

[1–5]

. The related research field covers the enhance-

ment mechanism of SERS as well as its applications as a

sensitive surface analytical tool for chemo/bio sensing

[3–5]

The mechanisms of the electromagnetic (EM) enhance-

ment induced by surface plasmon resonance usually

require a nanostructured metal substrate where the collec-

tive oscillation of the free electrons is confined, leading to

localized surface plasmon resonance (LSPR) under irradi-

ation of light

[6]

. The peak position and intensity of

LSPR can be strongly influenced by the roughness of the

prepared nanostructures.

Nanostructure plays an important role in producing

high-intensity scattering signals because it increases the

surface roughness and facilitates the generation of “hot

spots” that existed between adjacent nanoparticles (NPs)

and greatly enhances the EM field around them. Over the

past decade, most SERS substrates have been manufac-

tured by the conventional lithographic method; hence,

the development of cost-effective and simple procedures

to create nanostructured surfaces is attracting more atten-

tion in the SERS research field. The advancement in fem-

tosecond (fs) laser technology has opened new possibilit ies

for cost-effective fabrication of nanostructures on most

solid materials

[7–12]

More recently, fs laser-irradiated silicon wafers with

diverse surface morphologies have been reported to yield

high SERS enhancement factors (EFs) when coated with

thin film

[13]

and used in conjunction with methods such as

lithography

[14]

or nanosecond laser processing

[15,16]

. It has

also been demonstrated that the nanostructures formed

by the laser processing in silver nitrate solutions can

produce high EFs

[17–19]

. Despite these advantages, in nano-

second laser processing it is often difficult to control the

signal homogeneity due to non-uniform thermal effects. In

the solution processing system, the suspended silicon

debris would disturb further fabrication to form a large

and uniform substrate. Moreover, the chemical instability

of silver is an intrinsic drawback. Although the EF of gold

is not as high as silver, the high chemical stability and

molecular compatibility are considerable advantages.

Therefore the current demand of reliable and low-cost

substrates with both large-scale uniformity and high

EFs have severely limited the use of SERS in most

applications.

In this Letter, we first propose a two-step approach that

effectively combines fs laser fabrication and the thermal

dewetting process to obtain a NP array distributed

throughout the micro/nano structure, as illustrated in

Fig.

1. The first step is to fabricate large and uniform

Fig. 1. Schematic fabrication process of SERS substrates.

COL 13(11), 111401(2015) CHINESE OPTICS LETTERS November 10, 2015

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