Performance Improvement of ZnSnO Thin-Film Transistors with Low-Temperature Self-Combustion Reaction

Round 1

Reviewer 1 Report

In this paper, authors developed low-temperature process for ZnSnO TFTs utilizing self-combustion reaction. The results are clear and meaningful. However, I feel that there are many points to be discussed more clearly. In this study, authors concluded that the ZnSnO TFT based on self-combustion reaction is better than that with conventional method. I think more experimental data and scientific discussion is needed. I suggest the publication of this paper after minor revision. Please see my comments below.

 

1. Authors should compare the crystallinity of con-ZTO and self-ZTO. Furthermore, chemical compositions of thin films should be compared. As well known, both information is quite critical to TFT performances. Regardless of combustion reaction, authors used different precursors, implying that two thin films may have different crystallinity and chemical composition.

 

2. In this paper, authors concluded that self-ZTO TFT is better than con-ZTO TFT. However, that is not always true since the self-ZTO TFTs exhibit negative V_th. For practical use, obtaining a positive V_th (>0) is of significance. It is expected that self-ZTO TFT possesses much higher electron density than con-ZTO. Sometimes, residual impurities trap the electrons and lower the mobility (see NPG Asia Materials (2017) 9, e359). However, if the two ZTO have largely different chemical composition, which can be also the reason for large difference in carrier density (electrical properties). Therefore, authors should clarify why the carrier density or Vth differs between two ZTO.

 

3. In my opinion, the manuscript should provide more information. As mentioned above, more discussion should be made in the manuscript. i.e., film density, film morphology, crystallinity, absorption coefficient, electrical properties, trap density, reliability, etc. Of course, authors do not need to add all data I mentioned. However, authors need to clarify what makes the con-ZTO and self-ZTO so different.

 

 I recommend the following papers related to defects in oxides.

 NPG Asia Materials (2017) 9, e359, APL Mater. 7, 022501 (2019).

 

I am looking forward to seeing your revised manuscript.

Author Response

Response to Reviewer 1 Comments

 

 

Thank you for your letter and for the reviewers’ comments concerning our manuscript entitled “Performance Improvement of ZnSnO Thin-Film Transistors with Low-Temperature Self-combustion Reaction” Those comments are all valuable and very helpful for revising and improving our manuscript, as well as the important guiding significance to our research. We have revised some descriptions and added some experiments and discussions by studying comments carefully. The responds to the reviewers' comments are as follows:

 

Point 1: Authors should compare the crystallinity of con-ZTO and self-ZTO. Furthermore, chemical compositions of thin films should be compared. As well known, both information is quite critical to TFT performances. Regardless of combustion reaction, authors used different precursors, implying that two thin films may have different crystallinity and chemical composition.


 

Response 1: In general, the crystallization temperature of ZTO is above 500 °C [Ref. doi.org/10.1002/aelm.202000195, doi.org/10.1063/1.1483104, doi.org/10.1063/1.1843286]. In the case of self-ZTO DAL TFT, the combustion reaction lowers the forming temperature of the thin film, and the crystallization temperature decreases. However, the reduction of crystallization temperature is unlikely to be large, thus it is difficult for self-ZTO DAL TFT to have a crystal structure [Ref.12 in manuscript]. Also, Considering the uniformity of performance, it is hard to determine the presence of a grain boundary. In addition, the self-ZTO DAL TFT is fabricated at considerably low temperature of 350 °C. Therefore, we predict that the con-ZTO DAL TFT and self-ZTO DAL TFT have the amorphous structure. For that reason, we believe that the ZTOs are amorphous states and we added that comments with references as reference 18,19 in manuscript [Line 69-60, 143 and 256-262, Ref.18, 19 in manuscript. Ref.18 was changed to Ref.20].

 The con-ZTO DAL TFT demonstrate optimal performance at 7:3 mole ratio [in manuscript Ref.17]. In case of the self-ZTO DAL TFT, it shows optimal performance at 5:5 mole ratio. They are mentioned in lines 55-57 of the manuscript with a reference. the self-Combustion exhibits optimal performance when fuel and oxidizer are dissolved in a 1:1 ratio, and thus Self-ZTO showed the most optimal performance at a 5:5 ratio [Ref.13 in manuscript]. In this regard, if you need results from the same mole ratio as Con-ZTO DAL TFT, we can give you the supplement data. After thin film deposition, actual composition was not analysed. However, we predict that their composition is different when compared the con-ZTO DAL TFT of 7:3 mole ratio and the self-ZTO DAL TFT of 5:5 mole ratio.

 

Point 2: In this paper, authors concluded that self-ZTO TFT is better than con-ZTO TFT. However, that is not always true since the self-ZTO TFTs exhibit negative Vth. For practical use, obtaining a positive Vth (>0) is of significance. It is expected that self-ZTO TFT possesses much higher electron density than con-ZTO. Sometimes, residual impurities trap the electrons and lower the mobility (see NPG Asia Materials (2017) 9, e359). However, if the two ZTO have largely different chemical composition, which can be also the reason for large difference in carrier density (electrical properties). Therefore, authors should clarify why the carrier density or Vth differs between two ZTO.

 

Response 2: The con-ZTO DAL TFT and self-ZTO DAL TFT showed optimal performance at 7:3 and 5:5 mole ratio. The self-ZTO DAL TFT has a higher Sn content than the con-ZTO DAL TFT, which leads to an increase of the electron carrier in thin film. Therefore, the V_th is shown to have shifted in the negative direction than the con-ZTO DAL TFT. Furthermore, we believe that a positive V_th can be obtained by controlling the mole ratio and will add these contents to the manuscript [Line 152-157 in manuscript]. Also, as mentioned in question 1, the chemical composition of the con-ZTO DAL TFT and self-ZTO DAL TFT was designed in optimal mole ratio. This information presents in line 55-57 with references [in manuscript Ref.13,17]. If you need results from the same mole ratio as Con-ZTO DAL TFT, we can give you the supplement data.

 

Point 3: In my opinion, the manuscript should provide more information. As mentioned above, more discussion should be made in the manuscript. i.e., film density, film morphology, crystallinity, absorption coefficient, electrical properties, trap density, reliability, etc. Of course, authors do not need to add all data I mentioned. However, authors need to clarify what makes the con-ZTO and self-ZTO so different.

 

Response 3: Compared the electrical performance of the Con-ZTO, Self ZTO has higher mobility and _ION/OFF value at annealing temperature of 350 °C. To discuss trap density more clearly, we need to focus on XPS results. The results of XPS show that the V_O ratio acting as carriers is higher in the self-ZTO DAL TFT than in the con-ZTO DAL TFT. Also, the self-ZTO DAL TFT gas lower the M-OH bond ratio than in Con-ZTO DAL TFT. The M-OH bond acts as a trap site (defect state) and interferes with carrier movement as an impurity in the thin film. Therefore, the self-ZTO DAL TFT has a higher M-O bond ratio and a lower M-OH bond ratio than the con-ZTO DAL TFT, resulting in fewer trap sites, which be considered to have superior film quality (Line 175-185). We presented the details about that and added suggested reference “NPG Asia Materials (2017) 9, e359, APL Mater. 7, 022501 (2019)” as reference 21 [Line 180-181 and 263-264, Ref.7,21 in manuscript].

 

We have tried our best to improve the manuscript and made some changes in the manuscript. We appreciate for editor and reviewers’ work earnestly, and hope that the correction will meet with approval, however, if there are other questions, we are willing to revise it again.

Once again, thank you very much for your comments and suggestion.

Best regards,

Ye-Ji Han

 

Author Response File: Author Response.pdf

Reviewer 2 Report

The authors fabricated a ZTO TFT at low annealing temperatures of 350 °C using self-combustion and compared the improved performance of self-ZTO with that of con-ZTO.  The experimental data were analyzed and explaned, and some conclusions were made. I just have two minor questions:

1. Line 86-87, sat, th, ON/OFF should be subscript;
2. "con-ZTO TFT" in Line 94 is the same as "con-ZTO DAL TFT" in Line 95? If so, why not use the same name? 

Author Response

Response to Reviewer 2 Comments

 

 

Thank you for your letter and for the reviewers’ comments concerning our manuscript entitled “Performance Improvement of ZnSnO Thin-Film Transistors with Low-Temperature Self-combustion Reaction” Those comments are all valuable and very helpful for revising and improving our manuscript, as well as the important guiding significance to our research. We have revised some descriptions and added some experiments and discussions by studying comments carefully. The responds to the reviewers' comments are as follows:

 

Point 1: Line 86-87, sat, th, ON/OFF should be subscript;

 

Response 1: We modified the subscript to reflect correct parameters “V_D, μ_sat,V_th,I_ON/OFF [Line 87-89 in manuscript].

 

Point 2: "con-ZTO TFT" in Line 94 is the same as "con-ZTO DAL TFT" in Line 95? If so, why not use the same name?

 

Response 2: “con-ZTO TFT and con-ZTO DAL TFT mean the same devices. To avoid confusion, we modified to the same name “con-ZTO DAL TFT”. Also, the “self-ZTO” is modified as “self-ZTO DAL TFT” [Line 96-100 in manuscript]. Furthermore, we corrected the numerical errors of I_ON/OFF found in table1 (All of ‘× 106’ or ‘× 105’ words were delated.) [Line 92, I_ON/OFF list of Table 1 in manuscript].

 

We have tried our best to improve the manuscript and made some changes in the manuscript. We appreciate for editor and reviewers’ work earnestly, and hope that the correction will meet with approval, however, if there are other questions, we are willing to revise it again.

Once again, thank you very much for your comments and suggestion.

Best regards,

Ye-Ji Han

 

Author Response File: Author Response.pdf