High–low Kelvin probe force spectroscopy for measuring the interface state density

• Ryo Izumi,
• Masato Miyazaki,
• Yan Jun Li and
• Yasuhiro Sugawara

Beilstein J. Nanotechnol. 2023, 14, 175–189, doi:10.3762/bjnano.14.18

• to the surface, forming an accumulation layer of electrons. When a small negative bias voltage is applied to the metal tip (Vdc < 0), electrons (majority carriers) in the semiconductor are depleted from the surface, forming a depletion layer. When a large negative bias voltage is applied to the metal

• depletion layer of the semiconductor and the capacitance due to the interface charge, respectively. The applied voltage is divided between the semiconductor and the gap, and the following equation is obtained: Therefore, the modulation frequency fm component of the electrostatic force Fele(fm) acting on the

• the semiconductor interface states. Now, the capacitance CD of the depletion layer of the MIS structure is given by CD = |dQs/dVs|. In the charge accumulation region, from Equation 9, CD is given by In the depletion region, from Equation 10, CD is given by In the inversion region, from Equation 11, CD

Utilizing the surface potential of a solid electrolyte region as the potential reference in Kelvin probe force microscopy

• Nobuyuki Ishida

Beilstein J. Nanotechnol. 2022, 13, 1558–1563, doi:10.3762/bjnano.13.129

• changes when a DC voltage is applied between the electrodes in a simple electrochemical cell, as shown in Figure 1a. After applying the DC voltage for some time, the electric field in the solid electrolyte becomes shielded by the formation of a Li-depletion layer on the positive electrode side and a Li

LED-light-activated photocatalytic performance of metal-free carbon-modified hexagonal boron nitride towards degradation of methylene blue and phenol

• Nirmalendu S. Mishra and
• Pichiah Saravanan

Beilstein J. Nanotechnol. 2022, 13, 1380–1392, doi:10.3762/bjnano.13.114

• photocatalytic process [24]. The MBN-80 also exhibited a lower LDB and charge transit time through the depletion layer (charge transit time ∝ (LDebye)2), meaning a lower recombination of the charge carriers leading to an enhanced photocatalytic activity [29]. The same could again be justified through the width

A chemiresistive sensor array based on polyaniline nanocomposites and machine learning classification

• Jiri Kroutil,
• Alexandr Laposa,
• Ali Ahmad,
• Jan Voves,
• Vojtech Povolny,
• Ladislav Klimsa,
• Marina Davydova and
• Miroslav Husak

Beilstein J. Nanotechnol. 2022, 13, 411–423, doi:10.3762/bjnano.13.34

• coefficient. The resistivity of these nanocomposites depends on the p–n depletion layer width on the interface between the n-type nanoparticles and the surrounding p-type PANi molecules. Gas sensing analysis The gas sensing characterizations of sensitive layers were performed using a custom-built apparatus

Morphology-driven gas sensing by fabricated fractals: A review

• Vishal Kamathe and
• Rupali Nagar

Beilstein J. Nanotechnol. 2021, 12, 1187–1208, doi:10.3762/bjnano.12.88

• structure, inherent rough surfaces, and gaps acting as diffusion channels. Gas-sensing mechanism of fractal structures There are a number of models to explain the function of conductometric SMO gas sensors. For instance, electron depletion layer (for n-type materials) or hole accumulation layer theory (for

A self-powered, flexible ultra-thin Si/ZnO nanowire photodetector as full-spectrum optical sensor and pyroelectric nanogenerator

• Liang Chen,
• Jianqi Dong,
• Miao He and
• Xingfu Wang

Beilstein J. Nanotechnol. 2020, 11, 1623–1630, doi:10.3762/bjnano.11.145

• external power source. Working mechanism of a PENG based on p-Si/n-ZnO NWs heterojunctions To illustrate the working mechanism of self-powered PDs, schematic diagrams for the different conditions are presented in Figure 2. In the dark, a depletion layer is formed at the heterojunction interface due to

High-responsivity hybrid α-Ag₂S/Si photodetector prepared by pulsed laser ablation in liquid

• Raid A. Ismail,
• Hanan A. Rawdhan and
• Duha S. Ahmed

Beilstein J. Nanotechnol. 2020, 11, 1596–1607, doi:10.3762/bjnano.11.142

• positive role of CTAB in increasing the depletion layer width and decreasing the e–h recombination process. The calculated on/off ratio at 5 V of the heterojunctions synthesized without and with CTAB was 42 and 517, respectively. The responsivity Rλ of the photodetector represent one of the most important

• to be 1.5 × 102% and 4.5 × 103% at 510 nm, respectively. This significant increase in the responsivity and quantum efficiency of the photodetector after CTAB addition can be ascribed to the widened depletion layer width and increased minority carrier diffusion length as well as to the large surface

Synthesis and acetone sensing properties of ZnFe₂O₄/rGO gas sensors

• Kaidi Wu,
• Yifan Luo,
• Ying Li and
• Chao Zhang

Beilstein J. Nanotechnol. 2019, 10, 2516–2526, doi:10.3762/bjnano.10.242

• air at 200 °C, the adsorbed oxygen atoms capture free electrons from the conduction band to form adsorbed oxygen anions (O2−, O−). In ZnFe2O4, an electron depletion layer is left, which will result in an increase of the resistance. Upon exposure to acetone, the acetone molecules will adsorb to the

Prestress-loading effect on the current–voltage characteristics of a piezoelectric p–n junction together with the corresponding mechanical tuning laws

• Wanli Yang,
• Shuaiqi Fan,
• Yuxing Liang and
• Yuantai Hu

Beilstein J. Nanotechnol. 2019, 10, 1833–1843, doi:10.3762/bjnano.10.178

• tuning performance on higher doped piezoelectric p–n junctions requires the prestress loadings to be applied closer to the interface of p- and n-zone. This study on a non-equilibrium process of piezoelectric p–n junctions has significance for piezotronics. Keywords: depletion layer; I–V characteristics

• and an n-type piezoelectric semiconductor. Based on the hypothesis of depletion layer and the introduction of an undetermined parameter wpiezo, they qualitatively obtained some new and interesting phenomena. Luo et al. [30] investigated the forward-bias I–V characteristics of a piezoelectric p–n

• potential remains almost unchanged in the two zones outside the depletion layer, the p-zone and the n-zone, and the electric field is almost vanishing there. Thus, the steady-state diffusion equation of minority carriers in the two zones has no terms related to the electric field. However, the situation

Selective gas detection using Mn₃O₄/WO₃ composites as a sensing layer

• Yongjiao Sun,
• Zhichao Yu,
• Wenda Wang,
• Pengwei Li,
• Gang Li,
• Wendong Zhang,
• Lin Chen,
• Serge Zhuivkov and
• Jie Hu

Beilstein J. Nanotechnol. 2019, 10, 1423–1433, doi:10.3762/bjnano.10.140

• from the conduction band of WO3. Surface-adsorbed oxygen ions (O2−, O−, O2−) and a thick electron depletion layer of WO3 will form, giving rise to a low conductivity via the loss of free electrons, as shown in Figure 12a. Conversely, when exposed to reducing gases (such as H2S, NH3 and CO), the redox

Wet chemistry route for the decoration of carbon nanotubes with iron oxide nanoparticles for gas sensing

• Hussam M. Elnabawy,
• Juan Casanova-Chafer,
• Badawi Anis,
• Mostafa Fedawy,
• Mattia Scardamaglia,
• Carla Bittencourt,
• Ahmed S. G. Khalil,
• Eduard Llobet and
• Xavier Vilanova

Beilstein J. Nanotechnol. 2019, 10, 105–118, doi:10.3762/bjnano.10.10

• the sensor is exposed to NO2, the response is mainly due to the CNTs. In this case, the iron oxide NPs contribute to the enhancement of the response via a reduction of their associated depletion layer when NO2 molecules adsorb on the surface of NPs, which increases the conductivity of the layer

Graphene-enhanced metal oxide gas sensors at room temperature: a review

• Dongjin Sun,
• Yifan Luo,
• Marc Debliquy and
• Chao Zhang

Beilstein J. Nanotechnol. 2018, 9, 2832–2844, doi:10.3762/bjnano.9.264

• transformed into O−. When the temperature is above 397 °C, the oxygen anions are converted into O2−. The reaction equations are as follows: For n-type semiconductors, the electrons will continue to be captured from the surface of the semiconductors so that the width of electron depletion layer increases when

• exposed to oxidizing gases, increasing the electrical resistance. The gas molecules act as electron donors to the semiconductors when exposed to reducing gases, meaning that the width of electron depletion layer decreases, which decreases the resistance of the sensor. For p-type semiconductors, the width

• and potential barriers in the composites due to the heterojunctions, one at the α-Fe2O3 grain boundaries and another at the interfaces of α-Fe2O3 and rGO. It appeared clear that O2 adsorption on the α-Fe2O3 grain boundaries modified the width of the α-Fe2O3 depletion layer, which conversely altered

Nanocomposites comprised of homogeneously dispersed magnetic iron-oxide nanoparticles and poly(methyl methacrylate)

• Sašo Gyergyek,
• David Pahovnik,
• Ema Žagar,
• Alenka Mertelj,
• Rok Kostanjšek,
• Miloš Beković,
• Marko Jagodič,
• Heinrich Hofmann and
• Darko Makovec

Beilstein J. Nanotechnol. 2018, 9, 1613–1622, doi:10.3762/bjnano.9.153

• probably the result of the depletion layer surrounding the nanoparticles, causing their flocculation to decrease the excluded volume of polymer chains [19][20][21][29]. To test if any of the added compounds stabilize the suspension of NPs in the PMMA polymer solution, the polymerization of MMA was

Enhanced photoelectrochemical water splitting performance using morphology-controlled BiVO₄ with W doping

• Xin Zhao and
• Zhong Chen

Beilstein J. Nanotechnol. 2017, 8, 2640–2647, doi:10.3762/bjnano.8.264

• carrier collection pathways, an increased volume ratio between depletion layer and bulk, enhanced light capture due to multiple light scattering in nanostructures, and a high surface area for photochemical conversion reactions. In this study, we describe the synthesis of morphology-controlled W-doped

• ultimately affects the solar-to-hydrogen efficiency. Nanostructured materials have been often employed to overcome this limitation [11], as they can shorten the carrier collection distance and increase the volume ratio between depletion layer and bulk. In addition, they also offer a high surface area for

Active and fast charge-state switching of single NV centres in diamond by in-plane Al-Schottky junctions

• Christoph Schreyvogel,
• Vladimir Polyakov,
• Sina Burk,
• Helmut Fedder,
• Andrej Denisenko,
• Felipe Fávaro de Oliveira,
• Ralf Wunderlich,
• Jan Meijer,
• Verena Zuerbig,
• Jörg Wrachtrup and
• Christoph E. Nebel

Beilstein J. Nanotechnol. 2016, 7, 1727–1735, doi:10.3762/bjnano.7.165

• depletion layer below and next to the Al contact [18][19]. By applying potentials on the Al-Schottky contact, the applied electric field in the depletion region of the Schottky junction induces a band bending modulation which shifts the Fermi-level over NV charge transition level and the charge state of

Nanostructured TiO₂-based gas sensors with enhanced sensitivity to reducing gases

• Wojciech Maziarz,
• Anna Kusior and
• Anita Trenczek-Zajac

Beilstein J. Nanotechnol. 2016, 7, 1718–1726, doi:10.3762/bjnano.7.164

• electronic structure by improving electron migration from titanium dioxide to tin dioxide and promotes oxygen molecule adsorption at the surface [34]. The as-formed heterojunction (n–n type) affects the response due to the formation of the accumulation/depletion layer and increases the potential barrier at

• carrier transfer occurs and formation of a charge depletion layer. The discrete SnO2 nanoparticle coating acts as an oxygen adsorber, which donates electrons and increases carrier concentration, creating a stronger n–p heterojunction. As a result, tin oxide may become the primary conductive path, which

• of a flower-like form doped with SnO2 nanoparticles can be attributed to gas sensing properties of tin dioxide. This archetypical sensor material affects the formation of the depletion layer at the surface. As a consequence, electron charge carriers have to overcome a high potential barrier formed at

A composite structure based on reduced graphene oxide and metal oxide nanomaterials for chemical sensors

• Vardan Galstyan,
• Elisabetta Comini,
• Iskandar Kholmanov,
• Andrea Ponzoni,
• Veronica Sberveglieri,
• Nicola Poli,
• Guido Faglia and
• Giorgio Sberveglieri

Beilstein J. Nanotechnol. 2016, 7, 1421–1427, doi:10.3762/bjnano.7.133

• prepared ZnO and RGO–ZnO structures towards acetone and ethanol at an operating temperature of 250 °C. Since ZnO is an n-type semiconductor, when it is exposed to air at elevated temperatures the oxygen molecules are adsorbed on the surface of the material generating the electron depletion layer. The

Ammonia gas sensors based on In₂O₃/PANI hetero-nanofibers operating at room temperature

• Qingxin Nie,
• Zengyuan Pang,
• Hangyi Lu,
• Yibing Cai and
• Qufu Wei

Beilstein J. Nanotechnol. 2016, 7, 1312–1321, doi:10.3762/bjnano.7.122

• formation of an ohmic contact between PANI and In2O3. Compared with pure PANI, the In2O3/PANI nanofibers reach a higher current due to the smaller width of the depletion layer between PANI and In2O3. Moreover, the addition of PANI reduced the width of the depletion layer at the interface and was helpful to

• been formed between PANI and In2O3 nanofibers, in which PANI is a p-type semiconductor and In2O3 nanofibers presents as an n-type semiconductor [21][27][34]. The changes of the depletion layer of the p–n heterojuction are shown in Figure 10. The width of the depletion section is related to the doping

• concentration [39]. With low concentration doping, it needs a sufficiently thick depletion layer to provide impurity atoms to build an internal field. Accordingly, on exposure to NH3, the protons from PANI are transferred to the NH3 molecules, which results in a widening of the depletion layer in the PANI

NO gas sensing at room temperature using single titanium oxide nanodot sensors created by atomic force microscopy nanolithography

• Li-Yang Hong and
• Heh-Nan Lin

Beilstein J. Nanotechnol. 2016, 7, 1044–1051, doi:10.3762/bjnano.7.97

• response, but longer recovery than sensor B. The first two benefits can be explained by two factors. One is that the ND in sensor A has a larger surface to volume ratio. The other is due to the fact that the depletion layer thickness after adsorption is roughly equal to the Debye length [5][17][38

Room temperature, ppb-level NO₂ gas sensing of multiple-networked ZnSe nanowire sensors under UV illumination

• Sunghoon Park,
• Soohyun Kim,
• Wan In Lee,
• Kyoung-Kook Kim and
• Chongmu Lee

Beilstein J. Nanotechnol. 2014, 5, 1836–1841, doi:10.3762/bjnano.5.194

• ) modulation of the depletion layer width and (2) the UV-activated adsorption, and desorption of NO2 species. Experimental Synthesis of ZnSe nanowires Similar to that previously described [31], ZnSe nanowires were synthesized on 3 nm-thick gold (Au) layer-coated, c-plane sapphire (Al2O3(0001)) substrates by

Evolution of microstructure and related optical properties of ZnO grown by atomic layer deposition

• Adib Abou Chaaya,
• Roman Viter,
• Mikhael Bechelany,
• Zanda Alute,
• Donats Erts,
• Anastasiya Zalesskaya,
• Kristaps Kovalevskis,
• Vincent Rouessac,
• Valentyn Smyntyna and
• Philippe Miele

Beilstein J. Nanotechnol. 2013, 4, 690–698, doi:10.3762/bjnano.4.78

• than unity, which points to an oxygen-rich stoichiometry of the studied samples. In oxygen-rich films Zn vacancies, oxygen interstitials and oxygen interstates can be formed [46]. The excess oxygen may also localize on grain boundaries to form a negative surface charge [54] and depletion layer. The

• electric field of the surface charge in the depletion layer would stimulate dissociation of excitons in ZnO [18][48]. The absorption spectra of ultrathin ZnO ALD films show that the defect states are present in the gap. The defect states at 3.08–3.14 eV formed by neutral Zn vacancies and oxygen

• oxygen adsorbed on the grain surface. Therefore, a growing UV–vis intensity ratio in ZnO PL being observed (Figure 5) a decrease of the bending of surface band and the depletion layer is expected if the UV–vis intensity ratio grows in ZnO PL. The photo-generated electrons and holes are known to be

Functionalised zinc oxide nanowire gas sensors: Enhanced NO₂ gas sensor response by chemical modification of nanowire surfaces

• Eric R. Waclawik,
• Jin Chang,
• Andrea Ponzoni,
• Isabella Concina,
• Dario Zappa,
• Elisabetta Comini,
• Nunzio Motta,
• Guido Faglia and
• Giorgio Sberveglieri

Beilstein J. Nanotechnol. 2012, 3, 368–377, doi:10.3762/bjnano.3.43

• . It is proposed that the ΔR/R enhancement in this case originates from the changes induced in the depletion-layer width of the ZnO nanoparticles that bridge ZnO nanowires resulting from THMA ligand binding to the surface of the particle coating. The heightened response and selectivity to the NO2

• chemisorption involves electronic charge transfer, functionalisation of the surface of a metal-oxide semiconductor gas sensor with an organic monolayer will strongly influence the electronic properties of the surface. Transfer of electron density into the semiconductor will reduce the depletion layer, which is

Structural, electronic and photovoltaic characterization of multiwalled carbon nanotubes grown directly on stainless steel

• Luca Camilli,
• Manuela Scarselli,
• Silvano Del Gobbo,
• Paola Castrucci,
• Eric Gautron and
• Maurizio De Crescenzi

Beilstein J. Nanotechnol. 2012, 3, 360–367, doi:10.3762/bjnano.3.42

• depletion layer are collected before reaching the electrode and recombine. Further improvements should be devoted to enhance the efficiency of the device by improving the quality of the metallic contact, to avoid parasitic additional resistances. Experimental A sheet of AISI 316-SS (30 × 40 mm2, from

Ultraviolet photodetection of flexible ZnO nanowire sheets in polydimethylsiloxane polymer

• Jinzhang Liu,
• Nunzio Motta and
• Soonil Lee

Beilstein J. Nanotechnol. 2012, 3, 353–359, doi:10.3762/bjnano.3.41

• -type semiconductor: O2(g) + e− → O2–(ad). This produces a depletion layer near the nanowire surface, resulting in an upward band bending near the surface. Due to the large surface-to-volume ratio, the adsorption of O2 significantly reduces the conductivity of the nanowires. UV-light illumination with a

• -section indicates a depletion layer near the surface; (c) Under UV illumination the oxygen molecules desorb from ZnO and diffuse into the molecule network. Illustration for the device fabrication process. Acknowledgements We thank the QUT Vice-Chancellor’s Research Fellowship for financially supporting

Schottky junction/ohmic contact behavior of a nanoporous TiO₂ thin film photoanode in contact with redox electrolyte solutions

• Masao Kaneko,
• Hirohito Ueno and
• Junichi Nemoto

Beilstein J. Nanotechnol. 2011, 2, 127–134, doi:10.3762/bjnano.2.15

• solution) negatively charged. As the result the band structure of the SC (both the valence band (VB) and the conduction band) is bent as shown in Figure 3. This curved portion of the band structure is called a space charge layer (also called a depletion layer, where electrons are depleted). Under this

• representation for the formation of continuous Schottky junctions with space charge layer (i.e., depletion layer, green region) and conduction band (CB, gray region) in a nanoporous n-TiO2 thin film formed at the interface with an aqueous electrolyte solution containing an electron donor. In the space charge