Vanishing Confinement Regime in Terahertz HgTe Nanocrystals Studied under Extreme Conditions of Temperature and Pressure

Abstract

While HgTe nanocrystals (NCs) in the mid-infrared region have reached a high level of maturity, their far-infrared counterparts remain far less studied, raising the need for an in-depth investigation of the material before efficient device integration can be considered. Here, we explore the effect of temperature and pressure on the structural, spectroscopic, and transport properties of HgTe NCs displaying an intraband absorption at 10 THz. The temperature leads to a very weak modulation of the spectrum as opposed to what was observed for strongly confined HgTe NCs. HgTe NC films present ambipolar conduction with a clear prevalence of electron conduction as confirmed by transistor and thermoelectric measurements. Under the application of pressure, the material undergoes phase transitions from the zinc blende to cinnabar phase and later to the rock salt phase which we reveal using joint X-ray diffraction and infrared spectroscopy measurements. We discuss how the pressure existence domain of each phase is affected by the particle size.

Mid-wave infrared sensitized InGaAs using intraband transition in doped colloidal II–VI nanocrystals

“…30 Furthermore, the transport is strongly dependent on the temperature, making the sample cooling a viable strategy to reduce the dark current as opposed to a pristine array of degenerately doped NCs. 12,18,19,24,31 The extracted activation energy is 163 meV (Figure S9), which corresponds to half of the intraband gap energy. This is the highest value reported for transport in intraband particles at this wavelength, highlighting the benefit of our geometry.…”

Theoretical and Experimental Advances in High-Pressure Behaviors of Nanoparticles

“…1.5–2.5 GPa from zinc blende (ZB) to cinnabar, a significantly higher phase transition pressure at ca. 2.9 GPa has been theoretically predicted for 15 nm HgTe NPs . Lee et al.…”

“…2.9 GPa has been theoretically predicted for 15 nm HgTe NPs. 79 Lee et al reported that the spinel zero-dimensional (0D) Zn 2 SnO 4 NPs are stable up to 40 GPa. However, one-dimensional (1D) Zn 2 SnO 4 nanostructures irreversibly transition into a new structure that is similar to the orthorhombic structure of CaFe 2 O 4 .…”

Dedoping of Intraband Silver Selenide Colloidal Quantum Dots through Strong Electronic Coupling at Organic/Inorganic Hybrid Interfaces

“…In this context, Ag 2 Se is a promising alternative IR semiconductor, having a narrow bulk bandgap of ∼0.05–0.18 eV . As nanoparticles, Ag 2 Se demonstrates extensive photoresponse tunability from the NIR to the long-wave infrared (LWIR) region of the electromagnetic spectrum by varying particle diameter in the range of 2.6–27 nm. − The NIR response emerges from the interband energy transition (“the band gap”, between the 1S h and 1S e states), while the MWIR and LWIR response is perceived to be the result of an intraband energy transition from the 1S e to 1P e state. − Intraband transitions in IR CQDs have been explored more extensively in the Hg chalcogenide literature, − suggesting that energy level filling and stable n-type doping is a result of band edge positions relative to the environmental Fermi level, E F,env . − …”