Thickness dependence of the room-temperature ethanol sensor properties of Cu2O polycrystalline films

被引:2
作者
Aparicio-Huacarpuma, B. D. [1 ,2 ]
Aragon, F. F. [1 ]
Villegas-Lelovsky, L. [2 ,3 ]
Soncco, C. M. [2 ]
Pacheco-Salazar, D. G. [2 ]
Guerra, J. A. [4 ]
Morais, P. C. [1 ,2 ,3 ,4 ,5 ]
da Silva, S. W. [1 ]
Coaquira, J. A. H. [1 ]
机构
[1] Univ Brasilia, Inst Phys, Appl Phys Div, BR-70910900 Brasilia, DF, Brazil
[2] Univ Nacl San Agustin Arequipa, Av Independencia S-N, Arequipa, Peru
[3] Univ Estadual Paulista, Phys Dept, IGCE, BR-13506900 Rio Claro, SP, Brazil
[4] Pontificia Univ Catolica Peru, Dept Ciencias, Secc Fis, Av Univ 1801, San Miguel 32, Lima, Peru
[5] Univ Catolica Brasilia, Genom Sci & Biotechnol, BR-70790160 Brasilia, DF, Brazil
关键词
thermal evaporation; room temperature gas sensor; Cu2O thin film; bandgap narrowing; thickness decreases; NANOCRYSTALLINE THIN-FILMS; CUPROUS-OXIDE; BAND-GAP; RESISTIVITY; COPPER; DEPOSITION; STRAIN; GROWTH; NI;
D O I
10.1088/1361-6528/ad47cc
中图分类号
TB3 [工程材料学];
学科分类号
0805 ; 080502 ;
摘要
This study investigates the fabrication process of copper thin films via thermal evaporation, with precise control over film thickness achieved through Z-position adjustment. Analysis of the as-fabricated copper films reveals a discernible relationship between grain size (< D >) and Z-position, characterized by a phenomenological equation < D >(n)(XRD)( Z ) = < D > (n)(0)[ 1 + 3 /2( r/ Z)(2) + 15/ 8( r/ Z)( 4) ], which is further supported by a growth exponent (n) of 0.41 obtained from the analysis. This value aligns well with findings in the literature concerning the growth of copper films, thus underlining the validity and reliability of our experimental outcomes. The resulting crystallites, ranging in size from 20 to 26 nm, exhibit a resistivity within the range of 3.3-4.6 mu Omega <middle dot> cm. Upon thermal annealing at 200 degrees C, cuprite Cu2O thin films are produced, demonstrating crystallite sizes ranging from similar to 9 to similar to 24 nm with increasing film thickness. The observed monotonic reduction in Cu2O crystallites relative to film thickness is attributed to a recrystallization process, indicating amorphization when oxygen atoms are introduced, followed by the nucleation and growth of newly formed copper oxide phase. Changes in the optical bandgap of the Cu2O films, ranging from 2.31 to 2.07 eV, are attributed mainly to the quantum confinement effect, particularly important in Cu2O with size close than the Bohr exciton diameter (5 nm) of the Cu2O. Additionally, correlations between refractive index and extinction coefficient with film thickness are observed, notably a linear relationship between refractive index and charge carrier density. Electrical measurements confirm the presence of a p-type semiconductor with carrier concentrations of similar to 10(14) cm(-3), showing a slight decrease with film thickness. This phenomenon is likely attributed to escalating film roughness, which introduces supplementary scattering mechanisms for charge carriers, leading to a resistivity increase, especially as the roughness approaches or surpasses the mean free path of charge carriers (8.61 nm). Moreover, ab-initio calculations on the Cu2O crystalline phase to investigate the impact of hydrostatic strain on its electronic and optical properties was conducted. We believe that our findings provide crucial insights that support the elucidation of the experimental results. Notably, thinner cuprite films exhibit heightened sensitivity to ethanol gas at room temperature, indicating potential for highly responsive gas sensors, particularly for ethanol breath testing, with significant implications for portable device applications.
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页数:12
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