This paper reports the design analysis of a microfabricatable mid-infrared (mid-IR) surface plasmon resonance (SPR) sensor platform. The proposed platform has periodic heavily doped profiles implanted into intrinsic silicon and a thin gold layer deposited on top, making a physically flat grating SPR coupler. A rigorous coupled-wave analysis was conducted to prove the design feasibility, characterize the sensor's performance, and determine geometric parameters of the heavily doped profiles. Finite element analysis (FEA) was also employed to compute the electromagnetic field distributions at the plasmon resonance. Obtained results reveal that the proposed structure can excite the SPR on the normal incidence of mid-IR light, resulting in a large probing depth that will facilitate the study of larger analytes. Furthermore, the whole structure can be microfabricated with well-established batch protocols, providing tunability in the SPR excitation wavelength for specific biosensing needs with a low manufacturing cost. When the SPR sensor is to be used in a Fourier-transform infrared (FTIR) spectroscopy platform, its detection sensitivity and limit of detection are estimated to be 3022 nm/RIU and ~70 pg/mm(2), respectively, at a sample layer thickness of 100 nm. The design analysis performed in the present study will allow the fabrication of a tunable, disposable mid-IR SPR sensor that combines advantages of conventional prism and metallic grating SPR sensors.

The ability to conduct the chemical analysis of materials with the nanoscale spatial resolution has been a long term thrust in many science and engineering communities. Although several techniques such as chemical force microscopy [1] and tip-enhanced Raman spectroscopy [2] have been developed for the nanoscale chemical analysis, there still exist technical challenges in routinely achieving a full spectrum of chemical information at the nanoscale. The main objective of this study is to propose a novel tip-based nanoscale infrared (IR) spectroscopy by combining the atomic force microscopy (AFM) and the Fourier-transformed infrared (FT-IR) spectroscopy.

This paper reports the design analysis of a novel doped-silicon infrared-surface plasmon resonance (IR-SPR) platform. The structure combines the advantages of both conventional grating and prism surface plasmon couplers while providing several intrinsic beneficial aspects. In combination with a Fourier transform infrared spectrometer, the biosensor is shown to compare favorably in trace analyte detection with visible range SPR devices while still maintaining the advantageous characteristics of IR-SPR. A numeric analysis of the structure was completed using a rigorous coupled wave analysis method to determine the geometric parameters of the diffraction grating as well as assess the sensor’s performance. Finite element analysis simulations were used to model the electromagnetic field distributions during the plasmon resonance. The results demonstrate that surface binding concentrations of biochemical species as small as 70 pg/mm2 can be measured. The large probing depth resulting from the IR spectrum facilitates the study of larger analyte (e.g. living cells). Additionally, the structure offers unequaled adaptability for a user’s specific biosensing needs while remaining inexpensive owing to the microelectromechanical systems (MEMS) batch protocols used in fabrication.

This article investigates the electrothermal properties and responses of a doped silicon microcantilever under periodic (ac) Joule heating. To this end, a numerical model using a finite element analysis (FEA) was implemented to compute the steady periodic solutions in the frequency domain. The FEA results agree well with the cantilever ac behavior that was not possible with a previous 1-D analysis. Based on the acquired ac characteristics of the heated cantilever, its feasibility as a probe for nanoscale property measurement was studied by comparing the 3ω voltage signals before and after sampling 449 fg of polyethylene directly on the cantilever. The 3ω signal of the sampled cantilever is considerably different from that of the bare cantilever, suggesting that sample properties can be determined using the processes discussed here. The heater size effect on the ac behavior of the cantilever was also investigated, confirming that the high frequency region is closely related with the thermal diffusion at the heater. The obtained results willexpand the characterization and functionality of microcantilevers leading to advancements in localized thermal analysis.