This effect becomes negligible at higher frequencies. Figure 5 PSi dielectric permittivity and loss tangent in frequency ranges 1 to 40 GHz and 140 to 210 GHz. The curves depict PSi dielectric permittivity (a) and loss tangent (b), extracted from broadband electrical measurements combined with simulations of CPW TLines integrated on the PSi substrate for the frequency ranges 1 to 40 GHz and 140

to 200 GHz. In overall, from the above, we can deduce that the dielectric permittivity of porous Si is almost constant in the studied frequency ranges. It also shows a continuity of the two curves, suggesting FDA-approved Drug Library mouse the same constant value in the frequency range 40 to 140 GHz. The loss tangent shows a slight decrease with frequency, while again there is continuity between the low- and high-frequency curves. Comparison of PSi with other RF and millimeter-wave substrates In order to demonstrate the high performance of porous Si for use as a substrate for RF and

millimeter-wave devices, a comparison was made between this substrate and three other substrates used in the same respect. Identical CPW TLines were integrated on the four different substrates, their S-parameters were measured, and the propagation constant for each line was extracted. Figure 6 shows the extracted values of signal attenuation (a) and quality factor (b) for the BMS345541 in vivo CPW TLines on the four different substrates. We deduce that the lines on the three substrates, trap-rich HR Si, PSi, and quartz, have better performance than those on the low-resistivity CMOS Si. More specifically, trap-rich HR-Si reduces losses from 4.8

to 1.6 dB/mm at 210 GHz, while PSi leads to a further decrease of the attenuation loss of 1.2 dB/mm at 210 GHz. Both the above substrates show similar performance with quartz, which is a non-Si, off-chip substrate. Figure 6 Attenuation (a) and quality factor (b) of CPW TLines on PSi compared with Erythromycin three other substrates. Comparison of signal attenuation and quality factor of CPW TLines on PSi (blue lines) compared to that of similar CPW TLines on trap-rich HR Si (green lines), quartz (dark red lines) and low-resistivity CMOS Si (orange lines) in the frequency range 140 to 210 GHz. The observed HSP inhibitor reduction of signal attenuation a and the increase of the quality factor Q of the CPW TLine on PSi versus bulk Si is attributed to the reduction of the material loss tangent and dielectric permittivity through nanostructuring. As shown previously by the authors, the achieved low permittivity of porous Si at high porosities shows advantages in many RF and millimeter-wave devices, namely, high-characteristic impedance of the CPW TLines [5], inductors operating at higher frequencies [29, 30] and antennas with reduced surface waves induced into the substrate can be obtained.