AFM topography imaging – Page 2 of 2 – Blog • by NanoWorld®

In the search for lead-free, Si-microfabrication-compatible piezoelectric materials, thin films of scandium-doped aluminum nitride (Al,Sc)N are of great interest for use in actuators, energy harvesting, and micro-electromechanical-systems (MEMS).*

While the piezoelectric response of AlN increases upon doping with Sc, difficulties are encountered during film preparation because, as bulk solids with completely different structures and large differences in cation radii, ScN (rock salt, cubic) and AlN (wurtzite, hexagonal) are immiscible. *

Consequently, (Al,Sc)N is inherently thermodynamically unstable and prone to phase segregation. Film preparation is further complicated by the technological requirement for polar [001] or [00 1̲] out-of-plane texture, which is achieved using a seeding layer.*

In the article “C-Axis Textured, 2–3 μm Thick Al0.75Sc0.25N Films Grown on Chemically Formed TiN/Ti Seeding Layers for MEMS Applications” Asaf Cohen, Hagai Cohen, Sidney R. Cohen, Sergey Khodorov, Yishay Feldman, Anna Kossoy, Ifat Kaplan-Ashiri, Anatoly Frenkel, Ellen Wachtel, Igor Lubomirsky and David Ehre propose a protocol for successfully depositing [001] textured, 2–3 µm thick films of Al0.75Sc0.25N.*

The procedure relies on the fact that sputtered Ti is [001]-textured α-phase (hcp). Diffusion of nitrogen ions into the α-Ti film during reactive sputtering of Al0.75,Sc0.25N likely forms a [111]-oriented TiN intermediate layer. The lattice mismatch of this very thin film with Al0.75Sc0.25N is ~3.7%, providing excellent conditions for epitaxial growth. In contrast to earlier reports, the Al0.75Sc0.25N films prepared in the current study are Al-terminated. Low growth stress (<100 MPa) allows films up to 3 µm thick to be deposited without loss of orientation or decrease in piezoelectric coefficient. *

An advantage of the proposed technique is that it is compatible with a variety of substrates commonly used for actuators or MEMS, as demonstrated here for both Si wafers and D263 borosilicate glass. Additionally, thicker films can potentially lead to increased piezoelectric stress/strain by supporting application of higher voltage, but without increase in the magnitude of the electric field. *

SEM, AFM, EDS, XRD and XPS techniques were used for the film characterization. For the nanoscale topography maps with atomic force microscopy (AFM) NanoWorld Pyrex-Nitride series PNP-TRS silicon nitride AFM probes were used in peak-force tapping^1® mode. *

Figure 3 from Asaf Cohen et al. “C-Axis Textured, 2–3 μm Thick Al0.75Sc0.25N Films Grown on Chemically Formed TiN/Ti Seeding Layers for MEMS Applications”: AFM images of (a) a (100) silicon wafer following cleaning procedures as described in the Materials and Methods section; (b) 50 nm-thick Ti film deposited on the wafer at 300 K; (c) the same film following exposure to N2 plasma at 673 K for 30 min. For the nanoscale topography maps with atomic force microscopy (AFM) NanoWorld Pyrex-Nitride PNP-TRS AFM probes were used in peak-force tapping mode1. * — Figure 3 from Asaf Cohen et al. “C-Axis Textured, 2–3 μm Thick Al0.75Sc0.25N Films Grown on Chemically Formed TiN/Ti Seeding Layers for MEMS Applications”: AFM images of (a) a (100) silicon wafer following cleaning procedures as described in the Materials and Methods section; (b) 50 nm-thick Ti film deposited on the wafer at 300 K; (c) the same film following exposure to N2 plasma at 673 K for 30 min.

*Asaf Cohen, Hagai Cohen, Sidney R. Cohen, Sergey Khodorov, Yishay Feldman, Anna Kossoy, Ifat Kaplan-Ashiri, Anatoly Frenkel, Ellen Wachtel, Igor Lubomirsky and David Ehre
C-Axis Textured, 2–3 μm Thick Al0.75Sc0.25N Films Grown on Chemically Formed TiN/Ti Seeding Layers for MEMS Applications
Sensors 2022, 22, 7041
DOI: https://doi.org/10.3390/s22187041

The article “C-Axis Textured, 2–3 μm Thick Al0.75Sc0.25N Films Grown on Chemically Formed TiN/Ti Seeding Layers for MEMS Applications” by Asaf Cohen, Hagai Cohen, Sidney R. Cohen, Sergey Khodorov, Yishay Feldman, Anna Kossoy, Ifat Kaplan-Ashiri, Anatoly Frenkel, Ellen Wachtel, Igor Lubomirsky and David Ehre is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third-party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/.

¹Peak Force Tapping® is a registered trademark of Bruker Corporation.

Boron doped diamond (BDD) has great potential in electrical, and electrochemical sensing applications. The growth parameters, substrates, and synthesis method play a vital role in the preparation of semiconducting BDD to metallic BDD. Doping of other elements along with boron (B) into diamond demonstrated improved efficacy of B doping and exceptional properties.*

In the article “Influence of B/N co-doping on electrical and photoluminescence properties of CVD grown homoepitaxial diamond films” Srinivasu Kunuku, Mateusz Ficek, Aleksandra Wieloszynska, Magdalena Tamulewicz-Szwajkowska, Krzysztof Gajewski, Miroslaw Sawczak, Aneta Lewkowicz, Jacek Ryl, Tedor Gotszalk and Robert Bogdanowicz describe how B and nitrogen (N) co-doped diamond has been synthesized on single crystalline diamond (SCD) IIa and SCD Ib substrates in a microwave plasma-assisted chemical vapor deposition process.*

The surface topography of the CVD diamond layers was investigated using atomic force microscopy (AFM), and Kelvin probe force microscopy (KPFM) was employed to measure the contact potential difference (CPD) to calculate the work function of these CVD diamond layers.*

Atomic force microscopy topography depicted the flat and smooth surface with low surface roughness for low B doping, whereas surface features like hillock structures and un-epitaxial diamond crystals with high surface roughness were observed for high B doping concentrations. KPFM measurements revealed that the work function (4.74–4.94 eV) has not varied significantly for CVD diamond synthesized with different B/C concentrations.*

NanoWorld ARROW-EFM conductive platinumirdidium5 coated AFM probes with a typical spring constant of 2.8 N/m and a typical resonant frequency of 75 kHz were used.*

Figure 2 from “Influence of B/N co-doping on electrical and photoluminescence properties of CVD grown homoepitaxial diamond films “ by Srinivasu Kunuku et al: AFM topography of B/N co-doped CVD diamond on (with fixed N/C = 0.02) SCD IIa; (a) B/C ∼ 2500 ppm (b) B/C ∼ 5000 ppm (c) B/C ∼ 7500 ppm, and KPFM CPD images of B/N co-doped CVD diamond (with fixed N/C = 0.02) on SCD IIa; (d) B/C ∼ 2500 ppm (e) B/C ∼ 5000 ppm (f) B/C ∼ 7500 ppm. NanoWorld Arrow-EFM platinumiridium coated AFM probes were used for the KPFM and surface topography measurements. — Figure 2 from “Influence of B/N co-doping on electrical and photoluminescence properties of CVD grown homoepitaxial diamond films “ by Srinivasu Kunuku et al:
AFM topography of B/N co-doped CVD diamond on (with fixed N/C = 0.02) SCD IIa; (a) B/C ∼ 2500 ppm (b) B/C ∼ 5000 ppm (c) B/C ∼ 7500 ppm, and KPFM CPD images of B/N co-doped CVD diamond (with fixed N/C = 0.02) on SCD IIa; (d) B/C ∼ 2500 ppm (e) B/C ∼ 5000 ppm (f) B/C ∼ 7500 ppm.

*Srinivasu Kunuku, Mateusz Ficek, Aleksandra Wieloszynska, Magdalena Tamulewicz-Szwajkowska, Krzysztof Gajewski, Miroslaw Sawczak, Aneta Lewkowicz, Jacek Ryl, Tedor Gotszalk and Robert Bogdanowicz
Influence of B/N co-doping on electrical and photoluminescence properties of CVD grown homoepitaxial diamond films
Nanotechnology (2022), 33 125603
DOI: https://doi.org/10.1088/1361-6528/ac4130

Please follow this external link to read the full article: https://doi.org/10.1088/1361-6528/ac4130

Open Access The article “Influence of B/N co-doping on electrical and photoluminescence properties of CVD grown homoepitaxial diamond films” by Srinivasu Kunuku, Mateusz Ficek, Aleksandra Wieloszynska, Magdalena Tamulewicz-Szwajkowska, Krzysztof Gajewski, Miroslaw Sawczak, Aneta Lewkowicz, Jacek Ryl, Tedor Gotszalk and Robert Bogdanowicz is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.