Review Reports

Round 1

Reviewer 1 Report

 

This work presents a study of conduction mechanism present in 6nm aluminum oxide, deposited by atomic layer deposition. To analyze the conduction mechanisms, this manuscript discusses about Ohmic conduction (OC), Poole-Frenkel emission (PFE), Schottky emission (SE) and trap assisted tunneling (TAT). Also the authors perform numerical simulations on current-voltage measurements to two metal-insulator-semiconductor (MIS) capacitors with different gate electrode areas (3.6x10^-5 cm², and 6.4x10^-5 cm²).

1. This work discusses about multiple mechanisms and extracted parameters from current-voltage measurement. It is good to study the conduction mechanism from multiple aspects. However, “extraordinary claims require extraordinary evidence”. There is overfitting occurring in the simulation, since there are too many parameters being discussed from two samples. The authors need to study more samples to verify the validity of the extracted parameters.

2. About the section of “Materials and Method”, the authors need to offer the picture of the samples and the method to perform the measurement. In this part, only the preparation of the samples is written.

3. Before the section of “Conclusions”, the authors need to discuss about the significance of this manuscript compared with other papers. From my point of view, I don’t see the originality of this paper and how it can provide guidance for the industry.

4. Besides, there are several typos in the text

a.       In line 44, it should be “with 400 um”, not “whit 400 um”

b.       In line 83, it should be “pressure”, not “pression”

c.       In figure 1, it should be “e-beam evaporation” for step 3

d.       In line 156, it should be “below”, not “bellow”

e.       In line 244, it should be “verified with”, not “verify whit”

In summary, I think this paper needs to be improved substantially before it can be accepted.

 

Author Response

Thank you for your comments. The authors appreciate the time dedicated to reviewing our
work.

Author Response File: Author Response.pdf

Reviewer 2 Report

The paper must be revised. There are some aspects which are unclear. Generally, it seems more a didactic book chapter rather than a research paper. In particular:

- Figure 2: the curves are difficult to interpret. Is there any parametric study? How many plots are within the graph? It should be two but it seems to be more. Please explain and correct the label as Area 1 and Area 2.

Additionally, since the work is based on different region for the (gate) current density as a function of the electric field, please insert some labels/lines/etc. to distinguish the different region/behaviour that the authors will discuss after.

About this point, it is very important both in the abstract and in the conclusions section that the authors say that the different mechanisms are found as a function of the electric field intensity because it is not clearly explained to the readers. Conversely, it is not clear as equation 9 should works. Is it composed by summing different contributions which are active/inactive according to the voltage? If yes, please correct equation (9) insted of (8), page 8, row 221 and provide the values of all the 4 fitting paramenters in Table 1.

- Please put in a table all the parameters used for the fitting procedure (not the exctracted ones but the others used for the simulations).

- Please revise figure 8 because the resolution is too low.

- From the experimental point of view: please give the deposition time instead of the number of working cycles for ALD.

- Finally, the English language needs a strong revision.

 

Author Response

Thank you for your comments. The authors appreciate the time dedicated to reviewing our
work.

Author Response File: Author Response.pdf

Reviewer 3 Report

The manuscript provides a study of conduction mechanisms present in ultrathin films of aluminum oxide (Al2O3), deposited by atomic layer deposition (ALD). The paper is properly written and properly presented, and, once the details below are tackled and the manuscript revised, I believe it would be a good fit for this journal.

Below are some changes that need to be carried out and properly addressed prior to publication:

1)      The introduction is too light and incomplete. In particular, the ALD technique has not been introduced, and no literature survey is done on the ALD of alumina. The author should properly introduce the technology and what has been done for alumina, by referring to some key papers in the field, eg: George, Chem. Rev. 2010, 110, 1, 111–131 ; Puurunen, Journal of applied physics 97 (12), 9, 2005 ; Chawla, Nanomaterials 9 (1), 88, 2019 ; Leskela and Ritala, Thin solid films, 409, 1 138, 2002…In addition, some studies of the electronic properties of ALD alumina have already been published in the literature, and should be referred to (eg Bissig et al, Small, 12, 38,5339, 2016)

 

2)      There are some links to references that are wrong. For example, line 40, the author describes the properties of alumina and claims that the material is widely used for microelectronic applications, but the only  reference given relates to the passivation of solar cells. Additional and more appropriate references should be added.

 

3)      At page 7, the author presents a simulation with a a n-type silicon substrate, 300 um of thickness, with a doping of 1x1015 atoms/cm3 , an Al2O3 film with 6 nm of thickness, and an aluminum layer, 400 nm of thickness, for gate electrode. It is well known that the interface state play a key role in the conduction mechanisms, the author should comment on it and include the interface in the model.

 

Author Response

Thank you for your comments. The authors appreciate the time dedicated to reviewing our
work.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

I appreciate that the authors add the discussion section. That highlights the importance and originality of this work.

This work can be accepted.

Author Response

Thank you for your comments.

The authors appreciate the time dedicated to reviewing our work.

Author Response File: Author Response.pdf

Reviewer 2 Report

The paper is surely improved, however the authors did not reply to some aspects highlighted in the review, such as deposition time for ALD and multiple curves in Fig. 2. Apart from this minor revisions, the paper is good for publication.

Author Response

Thank you for your comments. We include the time deposition.

A thin Al₂O₃ layer (thickness of 6 nm) is deposited using ALD technique at 250 °C for 8 minutes, with 40 working cycles, and a pressure of 0.2 Torr.

For each fabricated structure, different measurements were developed in order to ensure reproducibility and confirm the high quality of the deposited ultrathin film of Al₂O₃

The authors appreciate the time dedicated to reviewing our work.

Author Response File: Author Response.pdf