Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userTernary Nitride Semiconductors in the Rocksalt Crystal Structure
165
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
Inorganic nitrides with wurtzite crystal structures are well-known semiconductors used in optoelectronic devices. In contrast, rocksalt-based nitrides are known for their metallic and refractory properties. Breaking this dichotomy, here we report on ternary nitride semiconductors with rocksalt crystal structures, remarkable optoelectronic properties, and the general chemical formula Mg$_{x}$TM$_{1-x}$N (TM=Ti, Zr, Hf, Nb). These compounds form over a broad metal composition range and our experiments show that Mg-rich compositions are nondegenerate semiconductors with visible-range optical absorption onsets (1.8-2.1 eV). Lattice parameters are compatible with growth on a variety of substrates, and epitaxially grown MgZrN$_{2}$ exhibits remarkable electron mobilities approaching 100 cm$^{2}$V$^{-1}$s$^{-1}$. Ab initio calculations reveal that these compounds have disorder-tunable optical properties, large dielectric constants and low carrier effective masses that are insensitive to disorder. Overall, these experimental and theoretical results highlight Mg$_{G-3}$TMN$_{G-2}$ rocksalts as a new class of semiconductor materials with promising properties for optoelectronic applications.
rate research
Read More
We report the computational investigation of a series of ternary X$_4$Y$_2$Z and X$_5$Y$_2$Z$_2$ compounds with X={Mg, Ca, Sr, Ba}, Y={P, As, Sb, Bi}, and Z={S, Se, Te}. The compositions for these materials were predicted through a search guided by machine learning, while the structures were resolved using the minima hopping crystal structure prediction method. Based on $textit{ab initio}$ calculations, we predict that many of these compounds are thermodynamically stable. In particular, 21 of the X$_4$Y$_2$Z compounds crystallize in a tetragonal structure with $textit{I-42d}$ symmetry, and exhibit band gaps in the range of 0.3 and 1.8 eV, well suited for various energy applications. We show that several candidate compounds (in particular X$_4$Y$_2$Te and X$_4$Sb$_2$Se) exhibit good photo absorption in the visible range, while others (e.g., Ba$_4$Sb$_2$Se) show excellent thermoelectric performance due to a high power factor and extremely low lattice thermal conductivities.
Recently amorphous oxide semiconductors (AOS) have gained commercial interest due to their low-temperature processability, high mobility and areal uniformity for display backplanes and other large area applications. A multi-cation amorphous oxide (a-IGZO) has been researched extensively and is now being used in commercial applications. It is proposed in the literature that overlapping In-5s orbitals form the conduction path and the carrier mobility is limited due to the presence of multiple cations which create a potential barrier for the electronic transport in a-IGZO semiconductors. A multi-anion approach towards amorphous semiconductors has been suggested to overcome this limitation and has been shown to achieve hall mobilities up to an order of magnitude higher compared to multi-cation amorphous semiconductors. In the present work, we compare the electronic structure and electronic transport in a multi-cation amorphous semiconductor, a-IGZO and a multi-anion amorphous semiconductor, a-ZnON using computational methods. Our results show that in a-IGZO, the carrier transport path is through the overlap of outer s-orbitals of mixed cations and in a-ZnON, the transport path is formed by the overlap of Zn-4s orbitals, which is the only type of metal cation present. We also show that for multi-component ionic amorphous semiconductors, electron transport can be explained in terms of orbital overlap integral which can be calculated from structural information and has a direct correlation with the carrier effective mass which is calculated using computationally expensive first principle DFT methods.
Interest in inorganic ternary nitride materials has grown rapidly over the past few decades, as their diversity of chemistries and structures make them appealing for a variety of applications. Due to synthetic challenges posed by the stability of N2, the number of predicted nitride compounds dwarfs those that have been synthesized, offering a breadth of opportunity for exploration. This review summarizes the fundamental properties and structural chemistry of ternary nitrides, leveraging metastability and the impact of nitrogen chemical potential. A discussion of prevalent defects, both detrimental and beneficial, is followed by a survey of synthesis techniques and their interplay with metastability. Throughout the review, we highlight applications (such as solid-state lighting, electrochemical energy storage, and electronic devices) in which ternary nitrides show particular promise.
Ternary nitride materials hold promise for many optical, electronic, and refractory applications yet their preparation via solid-state synthesis remains challenging. Often, high pressures or reactive gasses are used to manipulate the effective chemical potential of nitrogen, yet these strategies require specialized equipment. Here we report on a simple two-step synthesis using ion-exchange reactions that yield rocksalt-derived MgZrN$_2$ and Mg$_2$NbN$_3$, as well as layered MgMoN$_2$. All three compounds show nearly temperature-independent and weak paramagnetic responses to an applied magnetic field at cryogenic temperatures indicating phase pure products. The key to synthesizing these ternary materials is an initial low-temperature step (300-450 $^{circ}$C) to promote Mg-M-N bond formation. Then the products are annealed (800-900 $^{circ}$C) to increase crystalline domains of the ternary product. Calorimetry experiments reveal that initial reaction temperatures are determined by phase transitions of reaction precursors, whereas heating directly to high temperatures results in decomposition. These two-step reactions provide a rational guide to material discovery of other bulk ternary nitrides.
Zinc-based nitride CaZn2N2 films grown by molecular beam epitaxy (MBE) with a plasma-assisted active nitrogen-radical source are promising candidates of next-generation semiconductors for light-emitting diodes and solar cells. This nitride compound has previously only been synthesized in a bulk form by ultrahigh-pressure synthesis at 5 GPa. Three key factors have been found to enable heteroepitaxial film growth: (i) precise tuning of the individual flux rates of Ca and Zn, (ii) the use of GaN template layers on sapphire c-plane as substrates, and (iii) the application of MBE with an active N-radical source. Because other attempts at physical vapor deposition and thermal annealing processes have not produced CaZn2N2 films of any phase, this rf-plasma-assisted MBE technique represents a promising way to stabilize CaZn2N2 epitaxial films. The estimated optical band gap is ~1.9 eV, which is consistent with the value obtained from bulk samples. By unintentional carrier doping, n- and p-type electronic conductions are attained with low carrier densities of the order of 1013 /cm3. These features represent clear advantages when compared with Zn-based oxide semiconductors, which usually have much higher carrier densities irrespective of their intentionally undoped state. The carrier mobilities at room temperature are 4.3 cm2/(Vs) for electrons and 0.3 cm2/(Vs) for hole carriers, which indicates that transport properties are limited by grain boundary scattering, mainly because of the low-temperature growth at 250 {deg}C, which realizes a high nitrogen chemical potential.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
