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Charge transport mechanisms and memory effects in amorphous TaNx thin films.

Spyropoulos-Antonakakis N, Sarantopoulou E, Drazic G, Kollia Z, Christofilos D, Kourouklis G, Palles D, Cefalas AC - Nanoscale Res Lett (2013)

Bottom Line: However, electrical characteristics between different or neighboring regions in the same amorphous nanostructure may differ greatly.The nitride films are grown either on Au (100) or Si [100] substrates by pulsed laser deposition at 157 nm in nitrogen environment.Furthermore, I-V characteristics of the a-TaNx film deposited on Au show significant hysteresis effects for both polarities of bias voltage, while for the film deposited on Si hysteresis, effects appear only for positive bias voltage, suggesting that with the usage of the appropriate substrate, the a-TaNx nanodomains may have potential use as charge memory devices.

View Article: PubMed Central - HTML - PubMed

Affiliation: National Hellenic Research Foundation, Theoretical and Physical Chemistry Institute, 48 Vassileos Constantinou Avenue, Athens 11635, Greece. esarant@eie.gr.

ABSTRACT
Amorphous semiconducting materials have unique electrical properties that may be beneficial in nanoelectronics, such as low leakage current, charge memory effects, and hysteresis functionality. However, electrical characteristics between different or neighboring regions in the same amorphous nanostructure may differ greatly. In this work, the bulk and surface local charge carrier transport properties of a-TaNx amorphous thin films deposited in two different substrates are investigated by conductive atomic force microscopy. The nitride films are grown either on Au (100) or Si [100] substrates by pulsed laser deposition at 157 nm in nitrogen environment. For the a-TaNx films deposited on Au, it is found that they display a negligible leakage current until a high bias voltage is reached. On the contrary, a much lower threshold voltage for the leakage current and a lower total resistance is observed for the a-TaNx film deposited on the Si substrate. Furthermore, I-V characteristics of the a-TaNx film deposited on Au show significant hysteresis effects for both polarities of bias voltage, while for the film deposited on Si hysteresis, effects appear only for positive bias voltage, suggesting that with the usage of the appropriate substrate, the a-TaNx nanodomains may have potential use as charge memory devices.

No MeSH data available.


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Double sweeping of voltage bias on different nanodomains of both a-TaNx films. (a) Positive and (b) negative voltage bias swept on four nanodomains (curves 1 to 4) of a-TaNx film deposited on Au. (c) Positive and (d) negative voltage bias swept on three nanodomains (curves 5 to 7) of a-TaNx film deposited on Si. In the first three figures, significant current hysteresis is observed, while in the last figure, hysteresis effects are negligible.
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Figure 6: Double sweeping of voltage bias on different nanodomains of both a-TaNx films. (a) Positive and (b) negative voltage bias swept on four nanodomains (curves 1 to 4) of a-TaNx film deposited on Au. (c) Positive and (d) negative voltage bias swept on three nanodomains (curves 5 to 7) of a-TaNx film deposited on Si. In the first three figures, significant current hysteresis is observed, while in the last figure, hysteresis effects are negligible.

Mentions: Next, the two devices are double swept from -10 to 10 V to detect possible hysteresis phenomena, Figure 6. Indeed, pronounced current hysteresis of the retrace during the forward and reverse biasing cycle of the tip is identified only for the a-TaNx film on Au. The hysteretic loops are attributed to the conservation, during the bias voltage decrement process, of the internal electric fields caused by the stored space charges near the surface. Hysteresis, in this work, is defined as delta I at a fixed voltage. In Table 1, the hysteresis for the several I-V loops along with the calculated resistivity ratio at 3.5-V bias voltage where the resistivity ratio is quite high is shown. In Figure 6a,b, it is shown that all measured local points for a-TaNx deposited on Au, despite they demonstrate different conductivity, exhibit significant current hysteresis for positive and negative bias voltage. In contrast, for a-TaNx deposited on Si, positive voltage sweeping results in a resistivity ratio smaller than 3, Figure 6c, while hysteresis of the I-Vs for negative voltage sweeping is negligible, Figure 6d. This is consistent with the observed high-current and the low-voltage threshold, previously mentioned, which indicate low charge storage in that film.


Charge transport mechanisms and memory effects in amorphous TaNx thin films.

Spyropoulos-Antonakakis N, Sarantopoulou E, Drazic G, Kollia Z, Christofilos D, Kourouklis G, Palles D, Cefalas AC - Nanoscale Res Lett (2013)

Double sweeping of voltage bias on different nanodomains of both a-TaNx films. (a) Positive and (b) negative voltage bias swept on four nanodomains (curves 1 to 4) of a-TaNx film deposited on Au. (c) Positive and (d) negative voltage bias swept on three nanodomains (curves 5 to 7) of a-TaNx film deposited on Si. In the first three figures, significant current hysteresis is observed, while in the last figure, hysteresis effects are negligible.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4016540&req=5

Figure 6: Double sweeping of voltage bias on different nanodomains of both a-TaNx films. (a) Positive and (b) negative voltage bias swept on four nanodomains (curves 1 to 4) of a-TaNx film deposited on Au. (c) Positive and (d) negative voltage bias swept on three nanodomains (curves 5 to 7) of a-TaNx film deposited on Si. In the first three figures, significant current hysteresis is observed, while in the last figure, hysteresis effects are negligible.
Mentions: Next, the two devices are double swept from -10 to 10 V to detect possible hysteresis phenomena, Figure 6. Indeed, pronounced current hysteresis of the retrace during the forward and reverse biasing cycle of the tip is identified only for the a-TaNx film on Au. The hysteretic loops are attributed to the conservation, during the bias voltage decrement process, of the internal electric fields caused by the stored space charges near the surface. Hysteresis, in this work, is defined as delta I at a fixed voltage. In Table 1, the hysteresis for the several I-V loops along with the calculated resistivity ratio at 3.5-V bias voltage where the resistivity ratio is quite high is shown. In Figure 6a,b, it is shown that all measured local points for a-TaNx deposited on Au, despite they demonstrate different conductivity, exhibit significant current hysteresis for positive and negative bias voltage. In contrast, for a-TaNx deposited on Si, positive voltage sweeping results in a resistivity ratio smaller than 3, Figure 6c, while hysteresis of the I-Vs for negative voltage sweeping is negligible, Figure 6d. This is consistent with the observed high-current and the low-voltage threshold, previously mentioned, which indicate low charge storage in that film.

Bottom Line: However, electrical characteristics between different or neighboring regions in the same amorphous nanostructure may differ greatly.The nitride films are grown either on Au (100) or Si [100] substrates by pulsed laser deposition at 157 nm in nitrogen environment.Furthermore, I-V characteristics of the a-TaNx film deposited on Au show significant hysteresis effects for both polarities of bias voltage, while for the film deposited on Si hysteresis, effects appear only for positive bias voltage, suggesting that with the usage of the appropriate substrate, the a-TaNx nanodomains may have potential use as charge memory devices.

View Article: PubMed Central - HTML - PubMed

Affiliation: National Hellenic Research Foundation, Theoretical and Physical Chemistry Institute, 48 Vassileos Constantinou Avenue, Athens 11635, Greece. esarant@eie.gr.

ABSTRACT
Amorphous semiconducting materials have unique electrical properties that may be beneficial in nanoelectronics, such as low leakage current, charge memory effects, and hysteresis functionality. However, electrical characteristics between different or neighboring regions in the same amorphous nanostructure may differ greatly. In this work, the bulk and surface local charge carrier transport properties of a-TaNx amorphous thin films deposited in two different substrates are investigated by conductive atomic force microscopy. The nitride films are grown either on Au (100) or Si [100] substrates by pulsed laser deposition at 157 nm in nitrogen environment. For the a-TaNx films deposited on Au, it is found that they display a negligible leakage current until a high bias voltage is reached. On the contrary, a much lower threshold voltage for the leakage current and a lower total resistance is observed for the a-TaNx film deposited on the Si substrate. Furthermore, I-V characteristics of the a-TaNx film deposited on Au show significant hysteresis effects for both polarities of bias voltage, while for the film deposited on Si hysteresis, effects appear only for positive bias voltage, suggesting that with the usage of the appropriate substrate, the a-TaNx nanodomains may have potential use as charge memory devices.

No MeSH data available.


Related in: MedlinePlus