We report the final results of the Phase II SIMPLE measurements, comprising two run stages of 15 superheated droplet detectors each, with the second stage including an improved neutron shielding. The analyses include a refined signal analysis, and revised nucleation efficiency based on a reanalysis of previously reported monochromatic neutron irradiations. The combined results yield a contour minimum of $\sigma${}p=5.7\ifmmode\times\else\texttimes\fi{}10-3\,\,pb at 35\,\,GeV/c2 in the spin-dependent sector of weakly interacting massive particle (WIMP) proton interactions, the most restrictive to date for MW$\le${}60\,\,GeV/c2 from a direct search experiment and overlapping, for the first time, with results previously obtained only indirectly. In the spin-independent sector, a minimum of 4.7\ifmmode\times\else\texttimes\fi{}10-6\,\,pb at 35\,\,GeV/c2 is achieved, with the exclusion contour challenging a significant part of the light mass WIMP region of current interest.

Spin tunnel junctions with tunneling magnetoresistance of $\text{36.5\%±0.5\%,}$ resistance-area product of $\text{35±6\hspace{0.17em}}{\mathrm{k\Omega \times \mu m}}^{\mathrm{2}},$ and junction area between 6 and $\text{75\hspace{0.5em}}{\mathrm{\mu m}}^2$ were fabricated. The barrier height is $\text{2.5±0.3\hspace{0.17em}}\mathrm{eV}$ and the barrier thickness is $\text{7.7±0.3\hspace{0.17em}Å.}$ Large tunneling magnetoresistance (TMR) values are obtained by vacuum anneal (at temperatures from 100 to 240 °C for over 5 h) of junctions prepared with as-deposited TMR of $\text{21\%±1.7\%,}$ and an as-deposited resistance-area product of $\text{25±6\hspace{0.17em}}{\mathrm{k\Omega \times \mu m}}^{\mathrm{2}}.$ Two regimes occur during anneal. The first one occurs for anneals up to 200 °C where TMR and junction resistance increase, but the barrier parameters are unaltered. The second occurs above 200 °C, where TMR increases faster, together with an increase in barrier height. At 240 °C, TMR starts to decrease. Rutherford backscattering analysis indicates an asymmetry in the oxygen distribution in the as-deposited barrier. The oxygen distribution becomes homogeneous for anneals above 150 °C.

Phase II of SIMPLE (Superheated Instrument for Massive ParticLe Experiments) searched for astroparticle dark matter using superheated liquid ${\mathrm{C}}_{2}{\mathrm{ClF}}_{5}$ droplet detectors. Each droplet generally requires an energy deposition with linear energy transfer (LET) $$\gtrsim${}150\text{ }\text{ }\mathrm{keV}/$\mu${}\mathrm{m}$ for a liquid-to-gas phase transition, providing an intrinsic rejection against minimum ionizing particles of order ${10}^{$-${}10}$, and reducing the backgrounds to primarily $$\alpha${}$ and neutron-induced recoil events. The droplet phase transition generates a millimetric-sized gas bubble that is recorded by acoustic means. We describe the SIMPLE detectors, their acoustic instrumentation, and the characterizations, signal analysis and data selection, which yield a particle-induced, ``true nucleation'' event detection efficiency of better than 97% at a 95% C.L. The recoil-$$\alpha${}$ event discrimination, determined using detectors first irradiated with neutrons and then doped with alpha emitters, provides a recoil identification of better than 99%; it differs from those of COUPP and PICASSO primarily as a result of their different liquids with lower critical LETs. The science measurements, comprising two shielded arrays of fifteen detectors each and a total exposure of 27.77 kgd, are detailed. Removal of the 1.94 kgd Stage 1 installation period data, which had previously been mistakenly included in the data, reduces the science exposure from 20.18 to 18.24 kgd and provides new contour minima of ${$\sigma${}}_{p}=4.3\ifmmode\times\else\texttimes\fi{}{10}^{$-${}3}\text{ }\text{ }\mathrm{pb}$ at $35\text{ }\text{ }\mathrm{GeV}/{\mathrm{c}}^{2}$ in the spin-dependent sector of astroparticle dark matter\char21{}proton interactions and ${$\sigma${}}_{N}=3.6\ifmmode\times\else\texttimes\fi{}{10}^{$-${}6}\text{ }\text{ }\mathrm{pb}$ at $35\text{ }\text{ }\mathrm{GeV}/{\mathrm{c}}^{2}$ in the spin-independent sector. These results are examined with respect to the fluorine spin and halo parameters used in the previous data analysis.

The optoelectronic and structural properties of hydrogenated amorphous silicon-carbon alloys (a-SiC:H) are studied over the entire compositional range of carbon content. The films are prepared using low-power electron-cyclotron resonance (ECR) plasma-enhanced chemical vapor deposition. The carbon content was varied by using different methane (or ethylene-)-to-silane gas phase ratios and by introducing the methane (or ethylene) either remotely into the plasma stream or directly through the ECR source, together with the excitation gas (hydrogen). Regardless of the deposition conditions and source gases used, the optical, structural and transport properties of the a-SiC:H alloys followed simple universal dependencies related to changes in the density of states associated with their structural disorder. The deep defect density from photothermal deflection spectroscopy, the ESR spin density, the steady state and the transient photoluminescence, the dark and photoconductivity, the temperature of the hydrogen evolution peaks and the bonding from infrared spectroscopy are correlated to the Urbach tail energy, the B factor of the Tauc plot and $E_{04}$ (defined as the energy at which the absorption coefficient is equal to ${10}^4$ cm⁻¹). Silicon-rich and carbon-rich regions with very different properties, corresponding approximately to carbon fractions below and above 0.5, respectively, can be distinguished. The properties of the ECR a-SiC:H alloys are compared with those of alloys deposited by rf glow discharge.