Ultra-Hard (41 GPa) Isotopic Pure ¹⁰BP Semiconductor Microwires for Flexible Photodetection and Pressure Sensing

Abstract

An urgent demand for electronic and optoelectronic devices able to work in extreme environments promotes a series of research studies on semiconductor materials. Cubic boron phosphide (BP) as a semiconductor material with excellent characteristics shows great application potential. However, since the synthesis conditions required are difficult to achieve and the growth mechanism of BP is still unclear, there are few reports on the basic properties of BP and pure isotope BP, resulting in a narrow understanding of their special physical properties. Here, we successfully obtained highly pure isotopic 10 BP crystals by a vapor−liquid−solid (VLS) method unconventionally designed, which successfully overcomes the thermodynamic conflict between the high melting point of the boron element and low sublimation temperature of the phosphorus element. The 10 BP achieved owns an aspect ratio as high as 10 4 and a hardness up to 41 GPa. Besides, as an indirect bandgap semiconductor, it has ultrawide red emission spectra, a p-type conductivity with extremely low resistivity, and excellent photoelectronic and piezoelectric characteristics. Furthermore, compared with other superhard semiconductors like cubic BN and diamond, 10 BP has an obvious advantage of lower growth temperature (1200 °C). All these characteristics confirm the prospects owned by 10 BP in its applications to the field of high-conductivity, optoelectronic, strain-sensing, and superhard semiconductors.

Millimeter-Sized Monoisotopic Cubic 10Boron Phosphide

“…The binding energies (blue curves) of B 1s and P 2p in cubic nat BP are 187.95 and 130.00 eV, respectively, in good agreement with the values reported in previous literature. 3,16,17 The positions of P 2p and B 1s peaks in nat BP are both slightly higher than those in 10 BP, which is because the B in nat BP is composed of 80.1% 11 B and 19.9% 10 B, suggesting that the binding energy of both P 2p and B 1s will decrease with increasing 10 B concentration, that is, the B−P bonding in 10 BP is slightly lower than that in nat BP. This finding is similar to the previous results concerning isotopic hexagonal BN.…”

“…In recent years, the capabilities exhibited by isotopically enriched semiconductors in high thermal conductivity and efficient neutron interception have given this kind of material a special superiority in electronics industry and nuclear radiation detection. At present, element 10 B of the third main group has a comparatively higher isotope abundance and extensive compound semiconductors. − Isotopic materials for nuclear radiation detection can be gases, liquids, and solids. Compared with gas isotopes (mainly 3 He), devices made of solid isotope materials (usually containing elements 6 Li or 10 B) are advantageous due to the low working voltage and small device size, which makes solid-state materials more promising and suitable for nuclear radiation (neutron) detection .…”

Ultra-sharp-Line Emission in Isotopic c-10BP

“…Cubic boron phosphide (c-BP), as a member of the cubic boride family, has similar physical properties to those of c-BN and c-BAs, of which high thermal conductivity (540 W m –1 K –1 ) is an example. This commonality has prompted more research on this material in recent years, − but compared with c-BN and c-BAs, studies on the physical properties of c-BP are still lagging behind. For a deeper understanding of this material, in our previous work, micron-scale isotopic pure c-BP single crystals and micron wires were synthesized with detailed studies carried out on their properties such as the growth mechanism, lattice vibration, hardness, piezoelectricity, etc. − However, the difficulty of growing large-size high-quality single crystals hinders a further characterization of their physical properties at that stage.…”

Ultralarge Elastic Deformation (180° Fold) of Cubic-natBP Microwires for Wearable Flexible Strain Sensors

“…It is well-known that a phase diagram can provide the theoretical basis for crystal growth. 35 Here, based on the phase diagram of B−Ni, a pure cubic phase nat BP microwire is obtained by referring to the method of synthesizing isotropic c-10 BP micro-/nanowires reported previously, 36 that is, a gas− liquid−solid growth mechanism with single-boron powder and red phosphorus powder as the reactants and nickel as the catalyst, as illustrated in Figure 1. According to that B−Ni phase diagram, the solid−solution ratio of natural B in Ni can be modulated by controlling temperatures.…”