Thin film synthesis and properties of copper nitride, a metastable semiconductor

Caskey, Christopher M.; Richards, Ryan M.; Ginley, David S.; Zakutayev, Andriy

doi:10.1039/c4mh00049h

Cited by 130 publications

(145 citation statements)

References 50 publications

(58 reference statements)

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“…An RF-plasma atomic nitrogen source (HD25, Oxford Applied Research) run at 250 W and flowing 10 sccm of 99.999% purity N 2 gas was used to provide the reactive N* species for all films grown in this work. 20 Films were deposited on 50 x 50 mm Eagle XG glass substrates located 13 cm from the targets in a chamber with 10 -6 Torr residual water base pressure. Depositions were performed in a mixed Ar and N* atmosphere with 10 mTorr of each for a nominal chamber pressure of 20 mTorr.…”

Section: Methodsmentioning

confidence: 99%

Combinatorial insights into doping control and transport properties of zinc tin nitride

et al. 2015

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. Broader ContextThin film photovoltaics (PV), based on materials that absorb light 10-100 times more efficiently than crystalline silicon, has the potential to drive down PV module cost by increasing efficiency and requiring less raw material. Currently, the market for thin film PV is dominated by CdTe and CuIn x Ga 1-x Se 2 technologies, which suffer from concerns of toxicity (Cd) or rarity (Te, In) when considering terawatt-scale deployment. As an alternative to these technologies, researchers have turned to studying new absorber materials that exhibit equivalent light absorbing properties but are comprised of Earth-abundant elements. In this work, we explore the properties of a thin film III-N analog, ZnSnN 2 , that until recently has received little attention in the literature. Classification as a III-N analog is advantageous for PV applications, considering that III-N materials are well-known for their stability. ZnSnN 2 possesses a direct bandgap and large absorption coefficient in a PV-relevant energy range, in addition to being composed of abundant and non-toxic elements. However, a few key optoelectronic properties (e.g. doping control and exact bandgap) of this material are not well understood. If this challenge is addressed, ZnSnN 2 has excellent potential as an absorber material for Earth-abundant thin film PV. AbstractZnSnN 2 is an Earth-abundant semiconductor analogous to the III-Nitrides with potential as a solar absorber due to its direct bandgap, steep absorption onset, and disorder-driven bandgap tunability. Despite these desirable properties, discrepancies in the fundamental bandgap and degenerate n-type carrier density have been prevalent issues in the limited amount of literature available on this material. Using a combinatorial RF co-sputtering approach, we have been able to explore a growth-temperature-composition space for Zn 1+x Sn 1-x N 2 over the ranges 35-340• C and 0.30-0.75 Zn/(Zn+Sn). In this way, we were able to identify an optimal set of deposition parameters for obtaining as-deposited films with wurtzite crystal structure and carrier density as low as 1.8 x 10 18 cm -3 . Films grown at 230• C with Zn/(Zn+Sn) = 0.60 were found to have the largest grain size overall (70 nm diameter on average) while also exhibiting low carrier density (3 x 10 18 cm -3 ) and high mobility (8.3 cm 2

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Section: Methodsmentioning

confidence: 99%

Combinatorial insights into doping control and transport properties of zinc tin nitride

et al. 2015

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“…40 Another extreme case of reactive nitrogen precursors is atomic nitrogen, which can be made from the cracking of N 2 molecules in the plasma of reactive-sputtering processes. We previously used low-temperature reactive sputtering to synthesize thin-films of metastable Cu 3 N and Sn 3 N 4 semiconductors, 31,32 and determined from measured phase boundaries that this technique can yield nitrogen chemical potentials up to +1 eV/N above standard-state N 2 . A similar plasma-based synthesis was used to synthesize Na 3 N, which was also confirmed to be metastable.…”

Section: ■ Synthesis Strategy For Metastable Nitrogen-rich Nitridesmentioning

confidence: 99%

“…(2) We have experimentally demonstrated reactive sputtering with atomic nitrogen precursors as a technique to synthesize highly metastable nitride thin-films. 31,32 These two observations inspire the search for novel metastable nitrides in this relatively uncharted chemical space.…”

Section: ■ Introductionmentioning

confidence: 99%

Thermodynamic Routes to Novel Metastable Nitrogen-Rich Nitrides

et al. 2017

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Compared to oxides, the nitrides are relatively unexplored, making them a promising chemical space for novel materials discovery. Of particular interest are nitrogen-rich nitrides, which often possess useful semiconducting properties for electronic and optoelectronic applications. However, such nitrogen-rich compounds are generally metastable, and the lack of a guiding theory for their synthesis has limited their exploration. Here, we review the remarkable metastability of observed nitrides, and examine the thermodynamics of how reactive nitrogen precursors can stabilize metastable nitrogen-rich compositions during materials synthesis. We map these thermodynamic strategies onto a predictive computational search, training a data-mined ionic substitution algorithm specifically for nitride discovery, which we combine with grand-canonical DFT-SCAN phase stability calculations to compute stabilizing nitrogen chemical potentials. We identify several new nitrogen-rich binary nitrides for experimental investigation, notably the transition metal nitrides Mn 3 N 4 , Cr 3 N 4 , V 3 N 4 , and Nb 3 N 5 , the main group nitride SbN, and the pernitrides FeN 2 , CrN 2 , and Cu 2 N 2 . By formulating rational thermodynamic routes to metastable compounds, we expand the search space for functional technological materials beyond equilibrium phases and compositions.

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“…56,57 The films were grown on Corning Eagle XG glass substrates at a temperature of 260 • C. During deposition, the total pressure was kept at 1.6 Pa with a mass flow ratio f O 2 /( f O 2 + f Ar) of 1.75% for the Sn 1−x Zn x O films and 2.25% for the pure SnO film, respectively. It is necessary to reduce the oxygen partial pressure in the sputtering atmosphere, to suppress the change of Sn valence state from Sn 0 via Sn 2+ to Sn 4+ due to the addition of Zn during the SnO synthesis.…”

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confidence: 99%

Pathway to oxide photovoltaics via band-structure engineering of SnO

et al. 2016

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The prospects of scaling current photovoltaic technologies to terawatt levels remain uncertain. All-oxide photovoltaics could open rapidly scalable manufacturing routes, if only oxide materials with suitable electronic and optical properties were developed. A potential candidate material is tin monoxide (SnO), which has exceptional doping and transport properties among oxides, but suffers from a low absorption coefficient due to its strongly indirect band gap. Here, we address this shortcoming of SnO by band-structure engineering through isovalent but heterostructural alloying with divalent cations (Mg, Ca, Sr, Zn). Using first-principles calculations, we show that suitable band gaps and optical properties close to that of direct semiconductors are achievable in such SnO based alloys. Due to the defect tolerant electronic structure of SnO, the dispersive band-structure features and comparatively small effective masses are preserved in the alloys. Initial Sn 1−x Zn x O thin films deposited by sputtering exhibit crystal structure and optical properties in accord with the theoretical predictions, which confirms the feasibility of the alloying approach. Thus, the implications of this work are important not only for terawatt scale photovoltaics, but also for other large-scale energy technologies where defect-tolerant semiconductors with high quality electronic properties are required.

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Thin film synthesis and properties of copper nitride, a metastable semiconductor

Abstract: Copper nitride (Cu3N) thin films were grown by reactive sputtering using a high-throughput combinatorial approach with orthogonal gradients of substrate temperature and target–substrate distance.

Cited by 130 publications

References 50 publications

Combinatorial insights into doping control and transport properties of zinc tin nitride

Combinatorial insights into doping control and transport properties of zinc tin nitride

Thermodynamic Routes to Novel Metastable Nitrogen-Rich Nitrides

Pathway to oxide photovoltaics via band-structure engineering of SnO

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