Water Adsorption Enhances Electrical Conductivity in Transparent P-Type CuI

Crovetto, Andrea; Hempel, Hannes; Rusu, M.; Choubrac, Léo; Kojda, Danny; Habicht, K.; Unold, Thomas

doi:10.1021/acsami.0c11040

Cited by 23 publications

(30 citation statements)

References 41 publications

(107 reference statements)

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“…2c we plot the ratio between electrical conductivity and absorption coefficient as a function of lm composition, to obtain a simple but widely used gure of merit for transparent conductors. 53,77 In general, slightly P-poor compositions are benecial for both conductivity and transparency. On the other hand, increasing the Cu/ Ca ratio has a benecial effect on the conductivity but a detrimental effect on the absorption coefficient.…”

Section: Degenerate Defect Speciesmentioning

confidence: 99%

Prediction and realisation of high mobility and degenerate p-type conductivity in CaCuP thin films

et al. 2022

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Section: Degenerate Defect Speciesmentioning

confidence: 99%

Prediction and realisation of high mobility and degenerate p-type conductivity in CaCuP thin films

et al. 2022

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“…2,5,13,[20][21][22] A common figure of merit (FOM) for TCMs is the ratio between electrical conductivity and average absorption coefficient in the visible. 19,23 However, the absorption coefficient of BP has rarely been measured. Absorption coefficients of single crystals and single-crystalline films 13,14,20 are generally below 1 × 10 3 cm −1 at 2.5 eV, in line with computational predictions.…”

Section: Open Questions In Bp Research a Conductivity And Transparencymentioning

confidence: 99%

Boron phosphide films by reactive sputtering: Searching for a p-type transparent conductor

Crovetto¹,

Adamczyk²,

Schnepf³

et al. 2021

Preprint

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With an indirect band gap in the visible and a direct band gap at a much higher energy, boron phosphide (BP) holds promise as an unconventional p-type transparent conductor. Previous experimental reports deal almost exclusively with epitaxial, nominally undoped BP films by chemical vapor deposition. High hole concentrations were often observed, but it is unclear if native defects alone can be responsible for it. Besides, the feasibility of alternative deposition techniques has not been clarified and optical characterization is generally lacking. In this work, we demonstrate reactive sputtering of amorphous BP films, their partial crystallization in a P-containing annealing atmosphere, and extrinsic doping by C and Si. We obtain the highest hole concentration reported to date for p-type BP (5 × 10 20 cm −3 ) using C doping under B-rich conditions. We also confirm that bipolar doping is possible in BP. An anneal temperature of at least 1000 °C is necessary for crystallization and dopant activation. Hole mobilities are low and indirect optical transitions are much stronger than predicted by theory. Low crystalline quality probably plays a role in both cases. High figures of merit for transparent conductors might be achievable in extrinsically doped BP films with improved crystalline quality.

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“…[2,5,13,[21][22][23] A common figure of merit (FOM) for TCMs is the ratio between electrical conductivity and average absorption coefficient in the visible. [20,24] However, the absorption coefficient of BP has rarely been measured. Absorption coefficients of single crystals and single-crystalline films [13,14,21] are generally below 1 × 10 3 cm −1 at 2.5 eV, in line with computational predictions.…”

Section: Introductionmentioning

confidence: 99%

Boron Phosphide Films by Reactive Sputtering: Searching for a P‐Type Transparent Conductor

Crovetto

Adamczyk

Schnepf

et al. 2022

Adv Materials Inter

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eral applications such as a corrosion-and heat-resistant coating, [4,5] photo-and electrocatalyst, [6,7] as well as for thermal management [1] and extreme UV optics applications. [8] More recently, BP was identified as a potential p-type transparent conductive material (TCM). [9] This is a particularly interesting prospect, because obtaining high p-type conductivity in optically transparent materials is still an unsolved challenge. [10,11] Unlike the case of other p-type TCM candidates, bipolar doping has been reported in BP by various authors. [3,5,9,12,13] Thus, BP could be a unique example of a transparent material with both p-type and n-type doping capability. BP crystallizes in the diamond-derived zincblende structure with tetrahedral coordination. Because the electronegativity difference between B and P is small, BP is a covalent solid and its band structure is closely related to that of Si and C in the diamond structure. The main difference is an intermediate size of the fundamental indirect band gap for BP (≈2.0 eV) [14][15][16] mainly due to an intermediate bond length. Although this band gap corresponds to visible light, the direct band gap of BP is much wider and falls in the UV region (≈4.3 eV). [15][16][17] The weakness of indirect transitions predicted for BP at room temperature [15] is the key factor that could make BP thin films sufficiently transparent for many TCM applications. For example, a 100 nm-thick BP film is expected to absorb negligible amounts of red-yellow light and less than 10% of violet light according to first-principles calculations including electron-phonon coupling. [15] With respect to electrical properties, BP has a highly disperse valence band produced by p orbitals, ensuring low hole effective masses (0.35 m e ). [9] Unlike the case of diamond, the valence band maximum of BP lies at a relatively shallow energy with respect to the vacuum level. Shallow, disperse valence bands are usually correlated with high p-type dopability, due to easier formation of uncompensated shallow acceptor defects. [18,19] Open Questions in BP Research Conductivity and TransparencyThe highest conductivity reported for p-type BP is 3600 S cm −1 for a nominally undoped single-crystalline film deposited by chemical vapor deposition (CVD) at 1050 °C using B 2 H 6 and With an indirect band gap in the visible and a direct band gap at a much higher energy, boron phosphide (BP) holds promise as an unconventional p-type transparent conductor. This work reports on reactive sputtering of amorphous BP films, their partial crystallization in a P-containing annealing atmosphere, and extrinsic doping by C and Si. The highest hole concentration to date for p-type BP (5 × 10 20 cm −3 ) is achieved using C doping under B-rich conditions. Furthermore, bipolar doping is confirmed to be feasible in BP. An anneal temperature of at least 1000 °C is necessary for crystallization and dopant activation. Hole mobilities are low and indirect optical transitions are stronger than that predicted by theory. Low crystalline qua...

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Water Adsorption Enhances Electrical Conductivity in Transparent P-Type CuI

Cited by 23 publications

References 41 publications

Prediction and realisation of high mobility and degenerate p-type conductivity in CaCuP thin films

Prediction and realisation of high mobility and degenerate p-type conductivity in CaCuP thin films

Boron phosphide films by reactive sputtering: Searching for a p-type transparent conductor

Boron Phosphide Films by Reactive Sputtering: Searching for a P‐Type Transparent Conductor

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