  Using density functional theory calculations, we investigated the properties
of few-layer silicene nanosheets, namely bilayers and trilayers, functionalized
with group-III or group-V atoms of the periodic table. We considered the
Si$_2$X$_2$ bilayers and the Si$_2$X$_4$ trilayers, X = B, N, Al, P. We
computed the structural, energetic, dynamic, elastic, and electronic properties
of those systems in several stacking configurations, labeled as AA$'$, AB,
AA$'$A$''$, and ABC. The results revealed that AA$'$-Si$_2$N$_2$,
AB-Si$_2$N$_2$, AA$'$-Si$_2$P$_2$, AB-Si$_2$P$_2$, ABC-Si$_4$B$_2$,
ABC-Si$_4$Al$_2$, AA$'$A$''$-Si$_4$P$_2$, and ABC-Si$_4$P$_2$ nanosheets are
all dynamically stable, according to their respective phonon dispersion
spectra. Additionally, by comparing the standard enthalpies of formation of
doped few-layer silicene systems with the ones of the pristine silicene
monolayer, bilayer, and trilayer nanosheets, we found that those structures
could be experimentally accessed. Exploring the electronic properties of those
stable systems, we discovered that the silicene bilayers and trilayers
functionalized with N or P atoms change from a metallic to a semiconducting
behavior. However, the metallic behavior is kept when the nanosheets are
functionalized with B or Al atoms. Finally, by placing our results within the
context of silicon-based systems previous investigations, we could envision
potential applications for those nanosheets in van der Waals heterostructures,
alkali-metal ion batteries, UV-light devices, and thermoelectric materials.
