To meet the needs of high end gas sensing applications, new materials in suitable device designs are required that can challenge the state-of-the-art, especially concerning affinity towards target compounds within a complex background. Due to their high specific surface area and tailorable pore interiors, metal-organic frameworks (MOFs) serve as promising candidates to function as active coatings in next-generation sensors. However, studies on their integration in optoelectronic devices are rare due to the lack of suitable deposition methods. In this work, photonic crystal sensors functionalized with MOF thin films, are fabricated through a cleanroom-compatible process. The devices are capable of detecting low concentrations of volatile organic compounds, and thus, enable new avenues towards scalable fabrication and integration of miniature MOF-based gas sensor arrays.
Metal-organic frameworks (MOFs) are promising materials for next-generation gas sensing technologies. The implementation of MOFs into scalable gas sensor designs is, however, challenging due to high demands on the MOF film quality. Here, we report the highly sensitive detection of volatile organic compounds by transducing the gas adsorption in MOF thin films, prepared by chemical vapor deposition (MOF-CVD), into surface plasmon polariton shifts. Resonances as sharp as 14 nm, record-breaking shifts larger than 150 nm upon methanol uptake, and a limit of detection below 1 ppm are shown. These findings demonstrate the potential of MOF-CVD thin films for future gas sensing concepts.
The native self-alignment of area-selective deposition (ASD) processes makes this technology a promising solution for precise pattern positioning in the EUV era. The key challenge for any ASD process is its defectivity associated with the deposition on the growth-inhibiting surface. Therefore, the ability to qualify an ASD process using the appropriate set of in-line metrology tools is crucial for up-scaling of the technology. In this work, we present a new concept of area-selective ALD TiO2 growth and use it as an example to show the potential of in-line OCD and XPS tools for evaluation of ASD processes. The proposed novel process is based on selective growth of TiO2 on top of SiO2/SiN in the presence of plasma halogenated amorphous carbon (a-C:H) acting as a growth-inhibiting layer. The exposure of a-C:H to CF4 or Cl2 plasma results in formation of a thin halogen-rich film suppressing nucleation of TiO2, while the latter is minimally affected on the plasma treated SiNx or SiO2 layers. The selectivity was assessed on both blanket films and 45 nm half-pitch a-C:H line patterns. The analysis of blanket a-C:H substrates showed that the plasma chlorination provides a substantially more efficient growth inhibition as compared to the fluorination. However, the ability of the CF4-plasma to etch the topmost surface of the a-C:H makes it more favorable for application on a-C:H patterns, surface of which is typically contaminated with residues from hard-mask or from the patterning plasma. Therefore, the pre-cleaning of the a-C:H line pattern surface with CF4-plasma is required to restore the growth blocking efficiency of the chlorinated a-C:H.
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