Efficient tunable luminescence of SiGe alloy sheet polymers

Abstract

Crystalline SiGe alloy sheet polymers were topotactically prepared from epitaxially grown calcium germanosilicide Ca(Si1−xGex)2 precursor films in the whole composition range. These polygermanosilynes are found to be a well-defined mixture of the known siloxene and polygermyne sheet polymers with the OH groups exclusively bonded to silicon. The optical properties determined by photoluminescence and optical reflection measurements identify the mixed SiGe sheet polymers as direct semiconductors with efficient luminescence tunable in the energy range between 2.4 and 1.3 eV.

Two-dimensional gersiloxenes with tunable bandgap for photocatalytic H2 evolution and CO2 photoreduction to CO

“…The weak doublet peak at 780 and 845 cm −1 is due to GeH 2 bending modes from neighboring Ge atoms at the edges of each crystalline germanane sheet 24,42 . For Si 6 H 3 (OH) 3 , the bands observed at 519, 640, 876, 1056, 1638, 2116, and 3406 cm −1 correspond to the vibrations of ν(Si-Si), δ(Si-H), ν(Si-OH), ν (Si-O), ν(OH), ν(Si-H), ν((Si3)≡Si-H), and ν(OH) 43,44 , respectively. It can be seen from the FTIR spectrum ( Fig.…”

Silicon‐ and Germanium‐Based Sheet Polymers and Zintl Phases

“…Fourier-transform infrared spectroscopy (FTIR) and thermal effusion experiments (thermally programmed desorption, TPD) show that the hydroxyl groups are preferentially bonded to Si in the backbone rather than to Ge. [37] We therefore observe the overall topochemical transformation reactions…”

“…Indeed, such polygermanosilynes (Si 1-x Ge x H 1-y (OH) y ) n have been obtained over the entire composition range. [37] The different oxidation behavior of Si and Ge leads to a characteristic dependence of the OH concentration in the polygermanosilynes as a function of the Ge content x: For x < 0.5, the OH concentration is approximately constant. For x > 0.5, it decreases linearly to eventually become 0 in pure polygermyne.…”

“…Due to the much higher electrical conductivity of the sheet polymers parallel to the layers, [49] the latter orientation will be beneficial for the realization of optoelectronic devices where current flow across the Si/sheet polymer interface is required. We have analyzed the structure and the chemical composition of the Zintl phases, as well as of the sheet polymers, with the help of X-ray diffraction (XRD), [17,34,37,36,41,45,46,50] scanning electron microscopy (SEM), [45,46,51] energy dispersive X-ray analysis (EDX), [17,34,36,37] elastic recoil detection analysis (ERD), [46] nuclear magnetic resonance (NMR), [16,52] thermally programmed desorption (TPD), [37,51] and vibrational spectroscopy (Raman, infrared absorption and neutron scattering). [53,54] The strained epitaxial layers of CaSi 2 have also been used to study the elastic properties of this Zintl phase.…”

“…[74][75][76] Comparison of the dependences of the photoluminescence energies and the absorption edges of several Si 1-x Ge x compounds on the Ge content x. [26,37,62,77] Polygermyne has a strong infrared luminescence at 1.3 eV (Figure 16.4 (a) top), which can also be excited with a small Stokes shift. [17,71] shows that the photoluminescence peak of the polygermanosilynes is continuously tunable between 1.3 and 2.4 eV.…”